Planning my first PST mod and need some help

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Planning my first PST mod and need some help

Post by solarchatted »

Hi
Now I have a new ITF, things are 'clear' !

What I wish to do is the obvious mod to use PST as a Quark and use it on various scopes, including my AR152 F/6.5

My 'practical' questions:

1. Do I need to warm tube to unscrew it from PST? I do not wish to break anything or scratch tube!
2. I do not wish to cut original tube, what do I use that fits or step-down adaptors or even if I need to use PTFE ?
3. I do also not wish to modify any telescope [if possible] and simply modify PST and use it with a standard 2" nose piece, any clear procedure to do it 'clean' and without ruining the PST ? - i.e.so I can re-mount it, in case I need or want to re-sell it in the future, or use it as portable - I am a keeper!
4. future questions will be which filter to use in front of the larger AR152, that does not break the Bank?
I plan to mainly use it with my smaller scopes 72mm and 80mm and in theory I will not need the front filter and maybe just use a good Baader IR/UV one!
Maybe a 100mm [cost much less] and use it with all scopes and make a reducer for 152mm and still use 100mm
5. Is it really worth the hassle and expense? - well, it is if one does not wish to buy a DS expensive adaptor for PST and still be in the 'small' magnification.
This might be another solution - https://www.meade.com/coronado-30mm-blo ... rough.html - Straight through ?

You cannot have the best for very little and since I will never be able to afford to buy 'anything' expensive, I have to do as much as possible myself and using the PST with a new ITF and still a little 5-6mm hole!

I am really in a limbo, desiring something more powerful [when needed] and be able to use my telescopes without buying a Quark - I still need to see, how long they actually last - in particular the electronics!

In short, I need the less expensive and but DIY doable solution to use PST SS as a Quark, over my telescopes - AR152 F/6.5, AR102SX [short tube!] and SW 72ED.

I could use my old SW ST80 and modify it - I never use it now - but is is F/4 or get a cheap ~ £. 70 70mm F/10 and modify it as others have done.

It is all about a balance of money spent and 'real' results worth doing a mod or not and look at what others can afford to do!

Thank you for putting up with me.
Mauro

PS sorry if I might have mixed up anything, I am not stupid, but I am no expert in Solar and Optics


SolarChatted
https://astronomo.space/my-images/the-sun/
https://www.youtube.com/@Astronomo_Space

Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by solarchatted »

You can PM me, if you wish ...


SolarChatted
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https://www.youtube.com/@Astronomo_Space

Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by solarchatted »

Finally found a little time to look and yes the best tool is the car oil filter tool [the one with a belt to avoid scratches], to remove PST tube.

Which way?
The normal anticlockwise movement? With left hand holding body [or vice with padding!] and right hand turning left or towards me if parallel in front of me?

I might try and make an adaptor, modifying what I can find sizeable.


SolarChatted
https://astronomo.space/my-images/the-sun/
https://www.youtube.com/@Astronomo_Space

Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by marktownley »

Hi Mauro, have you tried unscrewing the gold tube by hand? I've had some PSTs that just unscrew with little force.

If you're going to use your existing scopes you will need to get them working at f10 for the PST etalon.


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Re: Planning my first PST mod and need some help

Post by Merlin66 »

Mauro,
I have a write up available for the PST mod drop me an email address for a copy.
A couple of critical things.
The etalon assembly must be positioned 200mm inside focus.
The etalon works in an f10 beam. If the donor scope is faster (f5) the aperture will be reduced.
Adaptors, front and rear are available.
An ERF is recommended (front or internal) above 60mm aperture.


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Re: Planning my first PST mod and need some help

Post by MalVeauX »

Hey Mauro,

Some PST's are a bear to open up and are glued. I have opened two of them now. One was hard. I scratched it up good. The other was easy, it just came apart. You can use things like a heat gun or hair dryer to help warm up bonds (glue) and gently work things until they give. The most important thing about taking apart a PST is to NOT ruin the etalon housing. It's delicate. After you remove the gold tube, you need to peel off the rubber around the tuner. There will be tape and a small screw. Mark where the screw was and the holes it lines up with so you can put it back exactly. But take all that out. THEN try and take off the etalon from the black box. This way you are not twisting the etalon housing and breaking that little screw, which will totally ruin the PST etalon housing tuner.

Ken (Merlin66) wrote the book on this. So check out his information.

Also, I have a log showing how I did mine, and what I've done with it. Also the adapters I bought from AOK Swiss and all that. More info here:

viewtopic.php?f=9&t=25420

Since you do not want to cut a tube and you're looking to do things inexpensively, I recommend you forget looking at big 150mm+ apertures. Instead, look at 102mm aperture achromats at best. You can get away with a Baader 2" HA 35nm filter as an ERF, or a Baader 2" Red CCD-IR Block filter as an ERF in front of the etalon housing using a 2" extension in front of it, in an unfocused beam of light to cut costs. The collimation lenses are F10 on the etalon, and require +/-200mm on both sides to reach focus. So you have to find a really short tube with a short focuser to avoid cutting a tube. But in reality you will need to just cut a tube most likely. Alternatively, you can get different collimation lenses to go to F8 or something. Another option to avoid cutting a tube is to get an F8 scope and then get a Baader Glasspath 1.25x corrector (typically used for binoviewers) to bring the scope to F10 natively. Then it will work for PST modding. Another option is to get a native F10 scope all together. Celestron's 102mm F10 Omni XLT is a great option and inexpensive. And again, you can block the heat with one of the 2" filters I mentioned just above. You will want to get a bigger blocking filter (Stage II mod), so a Coronado 10mm blocking filter is a good way to go. You are not likely going to use sensors much larger than 10mm anyways (mono sensors that is), so it should be fine. If you're at all worried and have larger sensors like M43 size, then get the 15mm filter. Since you're on a budget, I doubt these are options, so the 10mm filter will be good. Then, to match it, something like an ASI290MM camera or ASI178MM camera would be worth looking at.

Very best,


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Re: Planning my first PST mod and need some help

Post by solarchatted »

marktownley wrote: Tue Apr 09, 2019 8:08 pm Hi Mauro, have you tried unscrewing the gold tube by hand? I've had some PSTs that just unscrew with little force.

If you're going to use your existing scopes you will need to get them working at f10 for the PST etalon.
Sorry for very late reply, I went on holiday and then back to work, I am now getting back to it.

I did try - not too strongly - unscrew it by hand.

Then I go the leather puller and unscrewed it straight away and screwed it back in by hand.


SolarChatted
https://astronomo.space/my-images/the-sun/
https://www.youtube.com/@Astronomo_Space

Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by solarchatted »

MalVeauX wrote: Wed Apr 10, 2019 10:29 am Hey Mauro,

Some PST's are a bear to open up and are glued. I have opened two of them now. One was hard. I scratched it up good. The other was easy, it just came apart. You can use things like a heat gun or hair dryer to help warm up bonds (glue) and gently work things until they give. The most important thing about taking apart a PST is to NOT ruin the etalon housing. It's delicate. After you remove the gold tube, you need to peel off the rubber around the tuner. There will be tape and a small screw. Mark where the screw was and the holes it lines up with so you can put it back exactly. But take all that out. THEN try and take off the etalon from the black box. This way you are not twisting the etalon housing and breaking that little screw, which will totally ruin the PST etalon housing tuner....
Hi
Sorry for very late reply!

I am thinking either use a Bresser 102sx I have - but is a fast one at F/4.5 or get a ... I have seen cheap 100mm F10 easily modifiable ... !
The Celestron's 102mm F10 Omni XLT seems a very good choice.
What do you think of the Bresser 102SX? It is very short?

I think the first thing to do is to get the PST block ready to be used and then start playing with scopes!

A lot to think about.
Mauro

PS thanks for the links!


SolarChatted
https://astronomo.space/my-images/the-sun/
https://www.youtube.com/@Astronomo_Space

Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by marktownley »

Any of the 100mm f10 scopes are excellent for PST mods.


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Re: Planning my first PST mod and need some help

Post by solarchatted »

Thanks


SolarChatted
https://astronomo.space/my-images/the-sun/
https://www.youtube.com/@Astronomo_Space

Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by solarchatted »

I am 'slowly' getting along [time permitting] to understand 'the works' by testing and already the SCT focuser mod is better than PST standard setting - even using bath-tub splash-proof insulators as spacers within 1.25" adaptor to hold PST eyepiece holder! :P
With SCT focuser I already got rid of the PST block with prism that interferes with beam, in fact (as mentioned on another thread) I now have a clearer and brighter image as is ... but beam has intensified too.

One question, just to be sure - for the time being, is it OK to use a Meade series 4000 RED #25A filter + IR/UV in front of etalon at adaptor length - i.e. in out of focus beam?
I already used the #25A as it is with PST or SCT mod and it does help in certain circumstances - I guess when it hazy.
Then if necessary I will probably get a Baader 2" HA 35nm or a Baader 2" Red CCD-IR Block filter.


I understand also this way I will have heat currents ... not having an ERF in front of telescope ...

If I can get away with 25A, then next expense will be a 100mm ERF to use with AR152 (possibly).

I am just trying to have 2 scopes, PST standard (when needed) and a I can dismount PST and use (mostly) with a 100mm or the AR152.
I am not greedy, but I would like to put one foot inside the 'better' side of Solar.

Thanks for taking the time to help
M

See images with SCT mod - https://tinyurl.com/y5qfdrns - although it was clear, it was quite hazy and if I am not wrong used the RED #25A filter and got away with it ...


SolarChatted
https://astronomo.space/my-images/the-sun/
https://www.youtube.com/@Astronomo_Space

Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by AndiesHandyHandies »

Hi

I am in the process of doing the same PST 'Combat'.

Now I have a new ITF, things are 'clear' !

What I wish to do is the obvious mod to use PST as a Quark and use it on various scopes, including my AR152 F/6.5

My 'practical' questions:

1. Do I need to warm tube to unscrew it from PST? I do not wish to break anything or scratch tube!
Follow Merlins advice on removing the rubber ring and small screw. Two of us used a rubber filter wrench, held black box in vice and a small rubber filter wrench on the etalon. It moved when I used my hand on the Gold tube as well. Obviously its a lottery as to whether the gold tube comes off on its own or with the etalon even so. We managed to get the etalon off the black box.

I soaked the screws in the black box with ethanol for a day but I still wrecked one using a small rachet wrench and had to drill out the top. The grease on the prism slide migrates onto the prism and I wanted to put stops in the front of the black box and at the bottom of the blocker / eyepiece holder. We tried to get the eyepiece tube off. Only the top part with the Comb Blocker in came off. A blowtorch did not get the base to move. Rod had to turn up a little ring to push fit down the useless ribbing in the base and bodge on a repair washer and holding random rubber ring to make a stop. Looking down the Comb Blocker, with no front on the black box, there are reflections off the top and bottom of the prism so the stops help to hide those. Also as the prism is not coated there are lots of transmitted and reflected spots in the box. So I painted the front, bottom and lid Black2 and flocked the back sides where the worst reflections are.

It would be usefull if front ERFs are called DERF and intenal ones ERF and the actual Comb Blocker that as there does not seem to be a standard.
Refections of the Sun inside the telescope are an issue. Use on the Moon first, etalon only, to find the brightest reflections.
Then on the Sun look into the blocking filter with no eyepiece to see what reflactions there are.
In the Vixen VMC I had to stop stray daylight coming in, commercial Maks are not baffled well enough as they are struggling with fully illuminated field issues, and limit the light to whats being used.

Put on a long front baffle, put a baffle on the edge of the secondary, and the corrector lenses edges are not blackened, put a stop on the front of the rear baffle. Made a smaller one to start with and then found the Suns size on it and turned it down to that. With the black box and 5mm Comb Blocker you are observing off axis for proms so you do not want any other light to get in. I found that ribbed baffles in the SH Barlows used and the black box are useless. In the Barlows Rod turned them down to have forward and rear facing angled knife edges. An angle into the wall to act as a 'beam dump'. With the bit between turned down so the knige edge vignettes it and the sloping edge of the far knife edge then reflects the out of field light onto the Black2 wall opposite. For the black box Rod made a nice baffle after the PST etalon, bright reflections off the etalon as it reflects out of Comb light. You need to get to the point where there are just a few very thin bright rings, off the kinife edges, and the rest is black as possible. I have the Vixen and black box now so the Sun has a inky black background to the eye,imaging will probably show scatter, and with it just outside the field there is no light visible to the eye.

2. I do not wish to cut original tube, what do I use that fits or step-down adaptors or even if I need to use PTFE ?
AOK Swiss sells standard and custom adapters. I had a custom front one to T2 made for my Vixen VMC110. I am about to order a standard AOK Swiss rear PST to 2" adapter for a DS with Bobs H-alpha filters, one for proms and 2 for chromosphere? We have tried a Omega Bobs 1.5A (0.15nm) as a Comb Blocker and it worked. Its narrower than the PST one. It is a cosmetic second so some variations across it. And allows the full etalon aperture to be used.

3. I do also not wish to modify any telescope [if possible] and simply modify PST and use it with a standard 2" nose piece, any clear procedure to do it 'clean' and without ruining the PST ? - i.e.so I can re-mount it, in case I need or want to re-sell it in the future, or use it as portable - I am a keeper!
I have made the etalon into a 'Combat' by taking out the two lenses, they should be marked with an arrow or mark them and check which side the flat face goes. I have put a Omega Bobs 25.4mm 40nm ERF in the front. It blocks long IR the Baader 35 nm lets through and it has dimmer reflections. And a KG1 25.4mm in the back to protect the etalon. I have used the PST Combat on a 127mm refractor on its own, with black box on the back, with no issues. But I am using a 2" Baader IV-IR in the 2" extension tube set on front of the PST adapter about 13cm in front of the etalon as well to spread the heat rejection out. Good up to 7" I would think. I found a 48-43mm filter ring adaptor on the front worked to baffle reflections from the 7cm of focus tube in front of it. For visual I am using a 1.25" Beloptic UV-IR on KG3 in the eyepiece for additional safety.

4. future questions will be which filter to use in front of the larger AR152, that does not break the Bank?
I plan to mainly use it with my smaller scopes 72mm and 80mm and in theory I will not need the front filter and maybe just use a good Baader IR/UV one!
Maybe a 100mm [cost much less] and use it with all scopes and make a reducer for 152mm and still use 100mm
MarkT says he only uses his 127mm once a month, in the UK so I am sticking with a Lunt 110mm DERF I bought SH. 100mm clear in a holder. You can use the PST with a telescope shorter than F10 it just vignettes it to F10. Just use a DERF or stop to suit or internal ERF, though the external DERF is better but more expensive.

5. Is it really worth the hassle and expense? - well, it is if one does not wish to buy a DS expensive adaptor for PST and still be in the 'small' magnification.
This might be another solution - https://www.meade.com/coronado-30mm-blo ... rough.html - Straight through ?

You need to get a bigger Comb Blocking filter. Daystar use Andover filters 12.5 or 25.4mm as I recall. They are soft coated so need a good DERF/ERF up front to make them last and stored in a moisture free environment.
I am trying Omega Bobs 40nm 25.4mm ERF and one of his H-alpha 'seconds' filter 1.5A at the moment as the Comb Blocker.

On my 127mm F7.5 I tried a bodge to stop cutting the tube. I put a nose piece off a 2x ED barlow with T2 to 48mm infront of the AOK adapter / PST etalon and black box. With no PST lenses. I got a good image. Rod has tested Barlows at the position they need to be for the PST and black box on a double star and they give about 4x. So I was working at F30 straight through. Looks as good as Pedros images and with the Bobs H-alpha just dropped onto the Beloptik in the eyepiece good for chromosphere (needs to be in a tilting holder for Stage 2 Mod).
From the Daystar site the PST looks like 0.7A and with Bobs filter 0.5A.

The problem with the PST Etalon is it needs to be outside the focusser to tune it. So there may not be enough back focus when doing a Stage 1 mod as the black box needs 200mm back focus.
MarkT shared a cunning mod where you move the collimating lens up into the focus tube. There may be a slight issue with the 'collimated' beam drifting out?
On my Vixen VMC110 mod, PST lens vignettes F9.4 to F10, I gambled that I would reach focus doing that and I was lucky that it does, just.
Rod made me a push-in, masking tape filler, holder from an old barlow. And the PST Collimator lens held in a little nose piece Barlow holder with a plastic Celestron Moon filter holder pushed in to hold the PST lens, as they use 25.4mm filters. (Anyone found a Chinese metal holder for 25.4mm Moon filters?)

Rod gets a full sun with a 2250mm fl refractor through the PST. For rare good days I will try a F10 180mm Mak, fl1800mm, as it nearly fills the PST and using the full aperture helps reduce instrument angles for a larger sweet spot. All PST mods will only have a small sweet spot in the middle due to collimation off band, acceptance angles and instrument angles.

You cannot have the best for very little and since I will never be able to afford to buy 'anything' expensive, I have to do as much as possible myself and using the PST with a new ITF and still a little 5-6mm hole!
A stage 1 Mod does make things larger and have more resolution. Though the sweet spot if not central will drift out of view. You may need to centre the etalon, MarkT did make a custom ring but has lost the CNC file unfortunately.

I am really in a limbo, desiring something more powerful [when needed] and be able to use my telescopes without buying a Quark - I still need to see, how long they actually last - in particular the electronics!

You can use the PST as it is on any scope. With suitable DERF or ERF.
Move the collimator forward to save sawing up your scope to reach focus.
It vignettes less than F10 to F10. So you can use a 100mm DERF on the small scopes and the longer refractor for larger image.
You can use a weak barlow, Baader 1.25x glasspath seems popular, to make a faster scope F10.
Or use a shorter collimator and re-focusser on a faster scope to use its full aperture, matching singlets or achromatic doublets for better quality.
solarchatforum.com/viewtopic.php?f=9&t=24425&p=219615#p219615

For the PST as is MarkT uses a UV-IR to block IR as it softens the picture when imaging.
I use a 2" Beloptik UV-IR on KG3 to block all IR. With a 52mm to 48mm adapter.
www.diane-neisius.de/coronado_pst/index_E.html

In short, I need the less expensive and but DIY doable solution to use PST SS as a Quark, over my telescopes - AR152 F/6.5, AR102SX [short tube!] and SW 72ED.

I could use my old SW ST80 and modify it - I never use it now - but is is F/4 or get a cheap ~ £. 70 70mm F/10 and modify it as others have done.

It is all about a balance of money spent and 'real' results worth doing a mod or not and look at what others can afford to do!

An AOK Swiss front end adapter lets you do Stage 1 mods for £50ish. 48mm or T2.
You can move the front collimator lens forward to reach focus without cutting tubes down.
You can use a weak Barlow £95, or ES achromat? £75 on shorter F no scopes to reach F10. Remember to check its power used in front of the PST at its position inside focus.
Or you can replace the PST Collimator and re-focusser lenses to use all a shorter F No telescopes aperture.
You should block UV and all IR for your safety and to make Comb Blocker last longer.
Long IR KG3 or Omega Bobs 40nm 25.4mm ERF.

Andrew


Thank you for putting up with me.
Mauro

PS sorry if I might have mixed up anything, I am not stupid, but I am no expert in Solar and Optics


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Re: Planning my first PST mod and need some help

Post by solarchatted »

Hi
Just noticed your reply.

I thought it was not a reply ... there is no bold or italic to discern my typing to yours.

I will copy it it and do it, then I will see your answers clearly.

Thanks
M


SolarChatted
https://astronomo.space/my-images/the-sun/
https://www.youtube.com/@Astronomo_Space

Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by solarchatted »

BOLDED answers ... to help anybody else reading.

Hi
I am in the process of doing the same PST 'Combat'.
Now I have a new ITF, things are 'clear' !
What I wish to do is the obvious mod to use PST as a Quark and use it on various scopes, including my AR152 F/6.5

My 'practical' questions:

1. Do I need to warm tube to unscrew it from PST? I do not wish to break anything or scratch tube!
Follow Merlins advice on removing the rubber ring and small screw. Two of us used a rubber filter wrench, held black box in vice and a small rubber filter wrench on the etalon. It moved when I used my hand on the Gold tube as well. Obviously its a lottery as to whether the gold tube comes off on its own or with the etalon even so. We managed to get the etalon off the black box.

I soaked the screws in the black box with ethanol for a day but I still wrecked one using a small rachet wrench and had to drill out the top. The grease on the prism slide migrates onto the prism and I wanted to put stops in the front of the black box and at the bottom of the blocker / eyepiece holder. We tried to get the eyepiece tube off. Only the top part with the Comb Blocker in came off. A blowtorch did not get the base to move. Rod had to turn up a little ring to push fit down the useless ribbing in the base and bodge on a repair washer and holding random rubber ring to make a stop. Looking down the Comb Blocker, with no front on the black box, there are reflections off the top and bottom of the prism so the stops help to hide those. Also as the prism is not coated there are lots of transmitted and reflected spots in the box. So I painted the front, bottom and lid Black2 and flocked the back sides where the worst reflections are.

It would be usefull if front ERFs are called DERF and intenal ones ERF and the actual Comb Blocker that as there does not seem to be a standard.
Refections of the Sun inside the telescope are an issue. Use on the Moon first, etalon only, to find the brightest reflections.
Then on the Sun look into the blocking filter with no eyepiece to see what reflactions there are.
In the Vixen VMC I had to stop stray daylight coming in, commercial Maks are not baffled well enough as they are struggling with fully illuminated field issues, and limit the light to whats being used.


Put on a long front baffle, put a baffle on the edge of the secondary, and the corrector lenses edges are not blackened, put a stop on the front of the rear baffle. Made a smaller one to start with and then found the Suns size on it and turned it down to that. With the black box and 5mm Comb Blocker you are observing off axis for proms so you do not want any other light to get in. I found that ribbed baffles in the SH Barlows used and the black box are useless. In the Barlows Rod turned them down to have forward and rear facing angled knife edges. An angle into the wall to act as a 'beam dump'. With the bit between turned down so the knige edge vignettes it and the sloping edge of the far knife edge then reflects the out of field light onto the Black2 wall opposite. For the black box Rod made a nice baffle after the PST etalon, bright reflections off the etalon as it reflects out of Comb light. You need to get to the point where there are just a few very thin bright rings, off the kinife edges, and the rest is black as possible. I have the Vixen and black box now so the Sun has a inky black background to the eye,imaging will probably show scatter, and with it just outside the field there is no light visible to the eye.

2. I do not wish to cut original tube, what do I use that fits or step-down adaptors or even if I need to use PTFE ?
AOK Swiss sells standard and custom adapters. I had a custom front one to T2 made for my Vixen VMC110. I am about to order a standard AOK Swiss rear PST to 2" adapter for a DS with Bobs H-alpha filters, one for proms and 2 for chromosphere? We have tried a Omega Bobs 1.5A (0.15nm) as a Comb Blocker and it worked. Its narrower than the PST one. It is a cosmetic second so some variations across it. And allows the full etalon aperture to be used.

3. I do also not wish to modify any telescope [if possible] and simply modify PST and use it with a standard 2" nose piece, any clear procedure to do it 'clean' and without ruining the PST ? - i.e.so I can re-mount it, in case I need or want to re-sell it in the future, or use it as portable - I am a keeper!
I have made the etalon into a 'Combat' by taking out the two lenses, they should be marked with an arrow or mark them and check which side the flat face goes. I have put a Omega Bobs 25.4mm 40nm ERF in the front. It blocks long IR the Baader 35 nm lets through and it has dimmer reflections. And a KG1 25.4mm in the back to protect the etalon. I have used the PST Combat on a 127mm refractor on its own, with black box on the back, with no issues. But I am using a 2" Baader IV-IR in the 2" extension tube set on front of the PST adapter about 13cm in front of the etalon as well to spread the heat rejection out. Good up to 7" I would think. I found a 48-43mm filter ring adaptor on the front worked to baffle reflections from the 7cm of focus tube in front of it. For visual I am using a 1.25" Beloptic UV-IR on KG3 in the eyepiece for additional safety.

4. future questions will be which filter to use in front of the larger AR152, that does not break the Bank?
I plan to mainly use it with my smaller scopes 72mm and 80mm and in theory I will not need the front filter and maybe just use a good Baader IR/UV one!
Maybe a 100mm [cost much less] and use it with all scopes and make a reducer for 152mm and still use 100mm
MarkT says he only uses his 127mm once a month, in the UK so I am sticking with a Lunt 110mm DERF I bought SH. 100mm clear in a holder. You can use the PST with a telescope shorter than F10 it just vignettes it to F10. Just use a DERF or stop to suit or internal ERF, though the external DERF is better but more expensive.

5. Is it really worth the hassle and expense? - well, it is if one does not wish to buy a DS expensive adaptor for PST and still be in the 'small' magnification.
This might be another solution - https://www.meade.com/coronado-30mm-blo ... rough.html - Straight through ?

You need to get a bigger Comb Blocking filter. Daystar use Andover filters 12.5 or 25.4mm as I recall. They are soft coated so need a good DERF/ERF up front to make them last and stored in a moisture free environment.
I am trying Omega Bobs 40nm 25.4mm ERF and one of his H-alpha 'seconds' filter 1.5A at the moment as the Comb Blocker.

On my 127mm F7.5 I tried a bodge to stop cutting the tube. I put a nose piece off a 2x ED barlow with T2 to 48mm infront of the AOK adapter / PST etalon and black box. With no PST lenses. I got a good image. Rod has tested Barlows at the position they need to be for the PST and black box on a double star and they give about 4x. So I was working at F30 straight through. Looks as good as Pedros images and with the Bobs H-alpha just dropped onto the Beloptik in the eyepiece good for chromosphere (needs to be in a tilting holder for Stage 2 Mod).
From the Daystar site the PST looks like 0.7A and with Bobs filter 0.5A.


The problem with the PST Etalon is it needs to be outside the focusser to tune it. So there may not be enough back focus when doing a Stage 1 mod as the black box needs 200mm back focus.
MarkT shared a cunning mod where you move the collimating lens up into the focus tube. There may be a slight issue with the 'collimated' beam drifting out?
On my Vixen VMC110 mod, PST lens vignettes F9.4 to F10, I gambled that I would reach focus doing that and I was lucky that it does, just.
Rod made me a push-in, masking tape filler, holder from an old barlow. And the PST Collimator lens held in a little nose piece Barlow holder with a plastic Celestron Moon filter holder pushed in to hold the PST lens, as they use 25.4mm filters. (Anyone found a Chinese metal holder for 25.4mm Moon filters?)

Rod gets a full sun with a 2250mm fl refractor through the PST. For rare good days I will try a F10 180mm Mak, fl1800mm, as it nearly fills the PST and using the full aperture helps reduce instrument angles for a larger sweet spot. All PST mods will only have a small sweet spot in the middle due to collimation off band, acceptance angles and instrument angles.


You cannot have the best for very little and since I will never be able to afford to buy 'anything' expensive, I have to do as much as possible myself and using the PST with a new ITF and still a little 5-6mm hole!
A stage 1 Mod does make things larger and have more resolution. Though the sweet spot if not central will drift out of view. You may need to centre the etalon, MarkT did make a custom ring but has lost the CNC file unfortunately.


I am really in a limbo, desiring something more powerful [when needed] and be able to use my telescopes without buying a Quark - I still need to see, how long they actually last - in particular the electronics!

You can use the PST as it is on any scope. With suitable DERF or ERF.
Move the collimator forward to save sawing up your scope to reach focus.
It vignettes less than F10 to F10. So you can use a 100mm DERF on the small scopes and the longer refractor for larger image.
You can use a weak barlow, Baader 1.25x glasspath seems popular, to make a faster scope F10.
Or use a shorter collimator and re-focusser on a faster scope to use its full aperture, matching singlets or achromatic doublets for better quality.
solarchatforum.com/viewtopic.php?f=9&t=24425&p=219615#p219615

For the PST as is MarkT uses a UV-IR to block IR as it softens the picture when imaging.
I use a 2" Beloptik UV-IR on KG3 to block all IR. With a 52mm to 48mm adapter.
www.diane-neisius.de/coronado_pst/index_E.html


In short, I need the less expensive and but DIY doable solution to use PST SS as a Quark, over my telescopes - AR152 F/6.5, AR102SX [short tube!] and SW 72ED.

I could use my old SW ST80 and modify it - I never use it now - but is is F/4 or get a cheap ~ £. 70 70mm F/10 and modify it as others have done.

It is all about a balance of money spent and 'real' results worth doing a mod or not and look at what others can afford to do!

An AOK Swiss front end adapter lets you do Stage 1 mods for £50ish. 48mm or T2.
You can move the front collimator lens forward to reach focus without cutting tubes down.
You can use a weak Barlow £95, or ES achromat? £75 on shorter F no scopes to reach F10. Remember to check its power used in front of the PST at its position inside focus.
Or you can replace the PST Collimator and re-focusser lenses to use all a shorter F No telescopes aperture.
You should block UV and all IR for your safety and to make Comb Blocker last longer.
Long IR KG3 or Omega Bobs 40nm 25.4mm ERF.


Andrew


Thank you for putting up with me.
Mauro

PS sorry if I might have mixed up anything, I am not stupid, but I am no expert in Solar and Optics
Last edited by solarchatted on Wed Jun 19, 2019 3:13 pm, edited 1 time in total.


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Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
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Re: Planning my first PST mod and need some help

Post by solarchatted »

At present, I have already dismounted all parts and already done a SCT focuser Mod and it is very nice, but with a 'wobble' PST eyepiece into an adaptor.

See this post: viewtopic.php?t=26069#p235640

I am waiting for AOK Swiss adaptors posted yesterday and then I will play with my AR152 - which already has a home-made 100mm mask with added tin-foil to further reflect The Sun back.

I will report as soon as I have done my first 'learning' test - yes, I will also test focusing with a piece of paper before I fit any thin on the scope - including my eyes!
:lol:

Notes on SCT focuser mod - I wish I had more time doing tests properly.


Yes, I have read somewhere about the Baader 1.25x glasspath - interesting.
Yes, I have used a 2" UV-IR filter and it seems to soften when imaging ... true!


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Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
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Re: Planning my first PST mod and need some help

Post by solarchatted »

ADDITION: while having dinner and talking with my wife, I just remembered one 'possibly important thing - in my case' ... do I have to take the lens/lenses OFF the Tuner?
If so, tomorrow I will get a couple of plastic sealed bags from workshop and at night take them off and mark with pencil which one if front and back + which way if forward on both sides -if there are two lenses.

The kind of in focus but not really made me think of this, which I read somewhere, I do not remember in which case you should take it off, although Beta from AOK swiss mentioned Tuner having a 25mm FL - if I am not mistaken.


Hi
I finally had got the AOK Swiss front adaptor and also got the back one - supposed to be used with a BF10-30 etc.

I instead used the PST BF6 and placed it in the middle of the back adaptor.

I added a 3rd threaded hole and replaced original thumbscrews with 3x nylon ones - I also added some padding around the PST eyepiece [BF6] unit and used the 3 thumbscrews to centre it - when I can afford a BF10, I will get it.

I masked AR152 down to 100mm using a cardboard and covered the front with aluminium foil to reflect the sun.
I made it in a way it does click on the 3 internal adjusting screws [over the lens] and put dew shield back on as further holder - that works well.

Then fit 178M [+IR filter] + PST eyepiece holder [BF6] fit as above + back adaptor + PST tuner + front adaptor + IR filter + Meade 4000 Red filter.

The whole thing seems OK and not getting hot, just a bit worm and I tend to put the AR152 lens cap on once in a while [yes, I know I will get hot currents].

Having said that, I can get a 'sort of focus' with AR152 focuser out at about 31mm and of course I get a lot more photons and I tend to keep camera between 1ms-7ms - gain minimum [100] using Sharpcap.

BUT ... it is not a very good focus and I am guessing either the 100mm is too much or the PST eyepiece holder [BF6] is too much in or both!

I have tried to pull out the whole 'lets call it Quark!' about 1.5-2cm and focus seems slightly better.
I also pulled the PST eyepiece holder out about 10mm - no change.
Also tried adding AR152 star diagonal to give it more distance - no change.

I also tried AR152 visually [same tests as above] and the same thing happen, I focus at bout 60mm [focuser out] using a Zoom at 24mm.
i.e. PST + SCT focuser mod I tried was much better, in fact and as expected it bettered PST altogether, by getting rid of the black box!

The other day I caught a Prominence and I did take a short video - see here the one called PST mod 2.5 ! - https://astronomo.space/my-images/the-sun - you can see there it cannot focus properly and I am not that far off too.
Bear in mind that day it was very hazy and you can see gain is too high, I wanted to see if I could get this small prominence and I did!

As mentioned a few times, I am no expert on optics.

Any idea what I am doing wrong?

Thanks again all of you for helping me getting there and sorry if I take sometime to reply.
Mauro


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Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
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Re: Planning my first PST mod and need some help

Post by marktownley »

It will be all about spacing distances, this will be key. Some pictures of setup will help figure out what is going on.


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Re: Planning my first PST mod and need some help

Post by solarchatted »

Here is an image

I tried various distances for PST eyepiece holder and front 2" Tuner adaptor.

The focusing was around 31mm focuser out - going further back or forward was going out of focus.

The focus was not 'clearly' totally in focus ...

I am pleased I do not need to get lenses out of Etalon, therefore must be distances.

At present AR152 should be F/9.8 and normally - if am not wrong - the 178M focuses at around 32mm [possibly with the star diagonal at normal 152mm F/6.5.

Thanks
Mauro
Attachments
PST_MOD_2-5.jpg
PST_MOD_2-5.jpg (79.74 KiB) Viewed 31942 times


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Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
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Re: Planning my first PST mod and need some help

Post by solarchatted »

UPDATE

Today I managed to have an hour or so, to do some more Visual tests - Sky was clear enough for ab bit.

For what I gathered:

Problem 1 - Focusing


I added my 35mm Revelation 2" extension [to the setup in above image - before the Etalon] and it did focus a bit better with focuser about 12mm out [if I remember well].
I have been able to 'barely' see a nice thin Prominence [south for telescope].
I guess I need to get a 25mm 2" as it might be better and probably focus at 21mm focuser out.

Tried a 2x shorter Barlow on it [without 35mm extension] for a few minutes and it did barely focus - I am going stupid here.


Problem 2 - Reduce intensity


I believe I need a better/tighter RED filter, maybe the Baader but that costs - same with a 35nm Baader, better put money away for an ERF then - at least I will have the correct [external] filtering, no hot currents and SAFE ... in about 10 years time!!!

Sun light is way too intense as I cannot see any surface at all, never seen surface with this mod - I barely managed to see surface using 178M last time I tried
I cannot afford 100mm ERF, i.e. it means I will have to leave this mod for the time being and go back to PST mod 1.5! SCT focuser ... but this time use the self-built Quark!

Before that, I wish to re-test with 178M and the 35mm extension to see if it is in fact better with camera as well - probably better than visually, as I can adjust intensity.

There are sometime reflections and I guess it is to do with the RED + IR/UV filter filter before the Etalon = a blooming cheap mess!
I hate it when you cannot do things properly.

Will have to try.

Pity I cannot afford to use my AR152 - the best of all I have for The Sun !

This is not even time to try and sell what I do not use, a lot of people is with NO money, in need to feed the family first!

Sorry for crying!
It reminds me of an Italian 'humanity' film: 'We have only crying left' :lol:


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Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by Merlin66 »

I think you need to review the basics of the PST mod.
1. The front of the etalon must be positioned near as possible at -200mm inside the prime focus of the donor scope.
2. The final focus will then be very (very) close to 200mm behind the etalon assembly.
Check your fitting/ settings to see how close they are to these numbers.


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Re: Planning my first PST mod and need some help

Post by AndiesHandyHandies »

Hi

You cannot just put the PST Etalon assembly with the AOK Swiss adapter on the front of the focusser in a normal commercial telescope. It is very unlikely to have 200mm and the adaptor length in-focus from the position where a normal Plossl say is in focus on the Moon or a star. The Collimator will not be producing a collimated beam correctly where you have it.

There are only two ways I know to use a commercial scope with the PST Etalon without cutting some of the tube holding the focusser off.
1. Move the first lens in the PST Etalon assembly up the tube so that with the PST adaptor in the focusser and using the Black Box first in Stage 1 Mod mode you can get an eyepiece to show a focus on the Sun. Using the Black Box you are close to being 200mm after the Re-focusser lens.
2. Remove the lenses from the PST Etalon assembly and put a barlow before it. I tried a 2x Barlow and it worked. Because it was 200mm inside focus rather than 100mm I got 4x and my F7.5 worked at F30. It looked OK. F40 is ideal for an air-spaced etalon like the PST not in a collimated set up.

If you use the telescope focusser to get a moved Collimator lens 200mm in front of focus you need another focusser after the re-focussing lens, as in a Stage 1 Mod or an additional focusser in a stage 2 mod as above, so you can get an eyepiece or reducer for imaging to focus on the image 200mm behind the re-focussing lens.

In the original PST the Gold tube is made so the Collimator lens is fixed at 200mm insode the focus of the 40mm objective.

Andrew.

Andrew.


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Re: Planning my first PST mod and need some help

Post by solarchatted »

Hi both of you thank you for your time.

Yes, I got it now!

I am back to ... I cannot make or have a friend that can make me a flange to replace current one on AR152, so I can fit focuser 'possibly' 100mm more inwards.

It looks like it is time to save for a Lathe - second hand and make ALL adaptors myself - something I should have started about 20 years ago, as the flange is very large and most 'new' low-cost Lathe are allowing max 50mm width of any aluminium blocks to be worked on.

OK, I will exhamine what I can do myself once again and report.

I hope this threads will help others.


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Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by solarchatted »

Hi again
Just to keep updated - for others too, that have no previous knowledge/studied Optics and need help understanding.

Yes, it is the obvious ... the Etalon was off ...

I managed to push-fit Etalon/Tuner [including AOK Swiss adaptor with 2" IR/UV + Meade 4000 RED #25 Filter at the end of the focuser tube [internally] by simply adding spacers and slightly forced fit it in perfectly.

It actually is ~18.5cm from edge of 2" - 1.25" reducer, then added my home-made PST Eyepiece holder unit reducer and that is about another 6-10mm to the PST ITF [at the base of the PST eyepiece holder].

I tried visually with a Seben 12-24mm Zoom, 25mm eyepiece Kernel 8mm etc. - I also added a second 1.25" IR/UV filter at view side to further reduce rays - you can see there is a difference and that means I really need to get a ERF [if I can afford a 100mm - that is expensive] in front or get a 2" Baader RED/IR filter and fit it together with my RED one to increase filtering.

Anyway, I finally see some surface and much clearer Prominences - actually very nice visually - wow!

I then decided to get Laptop out with 178M and taken some images, but it was very hazy and mostly cloud-running weather here.

I dismounted AR152 F/6.5 focuser a few times to slightly adjust Etalon Tuner which was already nearly there and finally got a beautiful group of prominences. If I am not wrong they were South-West of SUN.

When I get time I will check if images are decent enough.

I can still see The Sun is VERY strong indeed and will need a good ERF, but first I need to solve the Etalon position - obviously cannot stay inside!
I do not think any modification would help much - you cannot really move focuser much. I can see even if [as I thought to try] I make a thick Plywood flange, focuser will only be 55mm inside - not much for Etalon - but I could still try to see what happens.

I might just remove lenses within Etalon and try a 2x Barlow - but adding optics will make things worse.

Then, last resort and easier is to get an F/10 telescope and cut it!

Mauro


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Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by Starry Jack »

What make is your AR152?


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Re: Planning my first PST mod and need some help

Post by marktownley »

solarchatted wrote: Wed Jul 10, 2019 3:48 pm Meade 4000 RED #25
Whhhhooooaaaaaaa!!!! DANGEROUS! This is absorptive filter, not dielectric. Stop using it, and don't use the PST mod until you have proper filtration / ERFs. This filter WILL crack and given you are using visually worries more.


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Re: Planning my first PST mod and need some help

Post by Merlin66 »

As well as the above important comment from Mark, remember you don’t need a focuser in front of the PST etalon. Once the etalon is correctly positioned at the -200mm in front of the prime focus it should not be moved.
Any focusing behind the etalon to accommodate the eyepiece/ camera can be achieved with a spacer and a simple helical focuser - I use a BORG helical with good success.
(I also use a full aperture Baader DERF on my 100mm PST mod)


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Re: Planning my first PST mod and need some help

Post by solarchatted »

Starry Jack wrote: Wed Jul 10, 2019 4:45 pm What make is your AR152?
The original Explorer Scientific - not the other versions that usually have a different focuser attachment - if I am not wrong.


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Re: Planning my first PST mod and need some help

Post by solarchatted »

marktownley wrote: Wed Jul 10, 2019 7:00 pm
solarchatted wrote: Wed Jul 10, 2019 3:48 pm Meade 4000 RED #25
Whhhhooooaaaaaaa!!!! DANGEROUS! This is absorptive filter, not dielectric. Stop using it, and don't use the PST mod until you have proper filtration / ERFs. This filter WILL crack and given you are using visually worries more.
I checked and it does not heat up much, it is slightly warm and I tend to put the cap on every time it is not used.

But I did understand your concerns, I already stopped using it this way - at least I got a grasp of what is going on.

... I thought the only difference between Baader RED + IR filter was simply like a Meade 4000 RED + IR/UV filter [which I have] ...


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Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by solarchatted »

Merlin66 wrote: Wed Jul 10, 2019 7:17 pm As well as the above important comment from Mark, remember you don’t need a focuser in front of the PST etalon. Once the etalon is correctly positioned at the -200mm in front of the prime focus it should not be moved.
Any focusing behind the etalon to accommodate the eyepiece/ camera can be achieved with a spacer and a simple helical focuser - I use a BORG helical with good success.
(I also use a full aperture Baader DERF on my 100mm PST mod)

OK, got it.

I am thinking to actually get a M48 2" extension or stepped extension [in parts 5+5+5 etc.] and extend the front of the Etalon by screwing bits in front of AOK Swiss Front adapter and screw the PST Etalon FRONT lens in it and push it down the AR152 Focuser until I reach best focus/position I can.

I think this is the best way in my case. :bow

I will not need to modify AR152 + Etalon Tuner is accessible.

I could see I was nearly there by simply push fit the Etalon at end of Focuser tube.

After I get the extension, I only need a good DERF 100mm [pffft expensive I know but probably the most important part - safety and good filtering.

If possible, tomorrow I will also try the Etalon [in front of the focuser] ' without both lenses ' + a 2x kind of shorty Barlow I have - just to see if that could work too.
Obviously the least lenses you have the better the image [semi-educated guess!].

... I have just unscrewed the front Etalon lens ... easy peasy ... and will prepare it with 2x Barlow - hopefully tomorrow morning or late afternoon today I can try it.


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Solar Gear:
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Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
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Re: Planning my first PST mod and need some help

Post by marktownley »

solarchatted wrote: Sat Jul 13, 2019 2:03 pm ... I thought the only difference between Baader RED + IR filter was simply like a Meade 4000 RED + IR/UV filter [which I have] ...
No, totally different beasts. The way the 4000 filter works is by absorbing energy, regardless of what configuration is used it will absorb energy and at some point crack. It also has a transmission of something like 25% at target (656nm) wavelength. It might be good for looking at Mars but solar is a whole different thing.


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Re: Planning my first PST mod and need some help

Post by marktownley »

solarchatted wrote: Sat Jul 13, 2019 2:14 pm If possible, tomorrow I will also try the Etalon [in front of the focuser] ' without both lenses ' + a 2x kind of shorty Barlow I have - just to see if that could work too.
No it won't work. Don't waste your time. Many have been here with the same thought.


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Re: Planning my first PST mod and need some help

Post by Merlin66 »

The most successful and probably easiest PST mods are where the donor OTA is adapted (focuser removed and OTA cut) to correctly position the PST etalon assembly at the design -200mm inside the prime focus.
Many other options are fraught with problems and difficulties.
Keep it simple, and safe.


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Re: Planning my first PST mod and need some help

Post by marktownley »

Merlin66 wrote: Sat Jul 13, 2019 4:27 pm Keep it simple, and safe.
Sage advice from Ken


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Re: Planning my first PST mod and need some help

Post by AndiesHandyHandies »

Hi,

DO NOT use absorbtive colour filters as ERFs AFTER an objective as they absorb heat. They are only safe mounted in front of an objective.
Dielectric filters are safer after an objective as they reflect most of the energy they are not designed to let through.
An external dielectric Baader D-ERF or a Baader internal ERF using 35nm 2" or 1.25" filters which use the same dielectric technology on clear glass will work the same. The coatings will absorb the same amount of energy, say 6%, of the input energy. Intensity does not matter, as long as the filter does not melt. So the SAME amount of noise as heat will be present in the SAME solid angle. How the heat is dissipated would make a difference. It would be interesting to see videos of the two types of filter in the same telescope to see the seeing difference. And identically processed stacked images of the same length videos. Would the internal ERF pick out less good frames? Would there be a significant difference in the processed final image? And is there a different external seeing level each works at? If you do not experience very good seeing where you are an internal ERF may do.

You say you are stopping the 152mm down to 100mm to get F10.

A 1.25" 35nm Baader filter would be enough as an internal ERF. I have used one on a 110mm Vixen VMC110 which with obstruction is equivalent. For visual I use a Beloptik 1.25" KG3 with UV-IR coating on the eyepiece for complete safety.
You can use a 2" Baader 35nm up to 6" as Astrograph says. (Daystar used just a 2" UV-IR on a 10" SC at an astro fair for several days with a Quark. Filters creaked a bit it is said.)

You can put the two PST lenses in 1.25" Celestron Moon filter holders. They must be Celestron or similar looking plastic ones to be American 25.4mm (1") glass filter size and the same size as the PST etalon lenses.

I have made my PST etalon into a Quark 'Combo' Prominence by putting a tilted Omega 40nm filter in place of the front collimator lens. This is equivalent to the Andover filter in the front of the Combo, which is a soft filter by the way so degrades easily.
I may put the Beloptik in the place of the Re-focusser lens to act as a safe dust filter for the back of the etalon.

This means I can use the PST 'Combat' in F30 mode as it is or suspend the Moon filter mounted Collimator lens in front and the Re-focusser behind in F10 collimation mode.

I have found some Blue Fireball adapters.
One is a T2 male to female pass through mounting with a 1.25" filter female thread within it.
The second is a M48 Male with a 1.25" filter female thread within it. Shame they do not do a pass through M48.

You can use the front AOK Swiss PST adapter as you have to mount the Collimation lens forward enough to reach the 200mm position.
The PST adator will fit in the telescope focusser and be locked in place.
Use a M48 to T2 adapter on the front of that. Add T2 extensions till with the T2 pass through and the Celestron 1.25" Moon filter mounted Collimator lens is 200mm infront of the telescopes original focus. Careful measuring to engineering standards.
I used a T2 to M48 adapter and then 2" extension rings to position a 2" UV-IR filter where it is nearly fully illuminated to reject 50%+ of the incoming light. As a dielectric filter just a few % is absorbed and it will be 'cold' as Astrograph reports like a 35nm Baader filter. The Omega 40nm blocks ALL IR and has less reflections than the Baader. As I still have several CM of focus tube in front of the 2" UV-IR I added a 48mm to 43mm step down filter ring, Black2 painted, to block reflections off the focus tube.
I have only done a quick Stage 1 Mod bodge with the front mounted Collimator, so I know I am on the re-focusser focal plane, so far but looks OK, need to do some measurements next.

This will then just be as the original PST with the Collimating lens 200mm inside the objective focus. You will not have to go 200mm from the PST front as you can use what back focus the telescope has as well. The most back-focus you have the better as the singlet Collimator has some divergence after it.

I have the rear AOK Swiss PST adapter which accepts a 2" barrel or extension tube. The Celestron 1.25" Moon filter mounted Re-focussing lens can be put into the Blue Fireball 48mm to 1.25" adapter screwed into the front of a 48mm extension tube or diagonal, where it will just be after the PST etalon.
All you need is a low profile focusser after the PST re-focusser lens to focus eyepieces or CCDs on the re-focussing lens focal plane.

No need for a lathe.


agenaastro.com/blue-fireball-t-t2-male-m28-5-female-thread-adapter-t-10.html

agenaastro.com/blue-fireball-m48-male-m28-5-female-adapter-m-01.html

Andrew.


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Re: Planning my first PST mod and need some help

Post by solarchatted »

AndiesHandyHandies wrote: Sat Jul 13, 2019 9:28 pm Hi,

DO NOT use absorbtive colour filters as ERFs AFTER an objective as they absorb heat. They are only safe mounted in front of an objective.
Dielectric filters are safer after an objective as they reflect most of the energy they are not designed to let through...
agenaastro.com/blue-fireball-m48-male-m28-5-female-adapter-m-01.html

Andrew.
Wow, what an informative post.

Do you have some images to actually see something of the above statements?

I hate it when I am half-knowing what I am doing.
Yes, marktownley I totally understand that - the Meade is a standard absorbing filter = danger, while Baader Red + IR is a dielectric = reflecting - same as in Electronics [my 'used to be' field] which actually is= deflecting.

Thank you
M

ps if you have the time, I do not wish to be imposing at all.


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Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by solarchatted »

Well, what an informative and helpful forum.
You are really great guys.

So much work for this and I am back thinking that my easiest bet is a good Donor scope then, like the afore-mentioned Bresser Messier AR-90/900 OTA [far less expensive] or Bresser Messier AR-102/1000 Hex-Focus [2" focuser better for AOK Swiss adaptor] Optical Tube Assemblies.

Better a second hand one, I am very ' not liking ' to cut a tube, not the cutting, I just do not like to ruin a decent telescope, but it seems more likely I need to do that!

Pffft - back to the drawing board again - thinking time! I have so many things to do and find little time to tinker with Solar - I just wish I had a telescope done by now - ready to be taken out and enjoyed...


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Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by solarchatted »

One thing I am not sure [regarding donor scopes].
If I get a F10 and cut it, do I still use the Etalon unit with AOK adaptors + original PST eyepiece holder as I did or not? See previous image

I am guessing all I need is to set the Etalon unit [with its lenses] ~200mm in-focus - which I guess it is not equal to 200mm cut [!] but I will have to check with a piece of paper where donor telescope focus is - i.e when it catches fire !!! and fit Etalon 200mm in that respect.

... by the way, when I fit the Etalon ' complete ' inside end of focuser - it was pretty decent - only problem I could not tune it and I also finally focused onto the surface - 178M was about 0.9ms or less - I think!


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https://www.youtube.com/@Astronomo_Space

Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by Merlin66 »

The front AOK adaptor is just a means of mounting the PST etalon to the donor scope.
The rear adaptor will need addition spacers to bring the the final focus to a position 200mm behind the PST etalon assembly.


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Re: Planning my first PST mod and need some help

Post by solarchatted »

Merlin66 wrote: Sun Jul 14, 2019 5:06 pm The front AOK adaptor is just a means of mounting the PST etalon to the donor scope.
The rear adaptor will need addition spacers to bring the the final focus to a position 200mm behind the PST etalon assembly.
OK, thanks.

In the meantime -after wasting 3 hours trying to find the PST gold tube - [it was in AOK box!], I have re-fit the SCT mod back on.

At least I have a SAFE 40mm Solar Telescope, better than the original PST.

This time with better and tight adaptors and will try and fine-tune the 200mm distance.
Getting that PST black box off is the best thing ever - it feels like having a 40mm Lunt now!


SolarChatted
https://astronomo.space/my-images/the-sun/
https://www.youtube.com/@Astronomo_Space

Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by solarchatted »

Hi
I am back to something that works ... I keep it on this thread as it has been gathering info to help others too.

This morning I set-up for re-testing my SCT mod and it works great - actually better [etalon seems better after I removed lenses once and put them back without doing anything - weird!] and it is a bit different and I now have ~200mm from centre of Etalon to tip of 2x Barlow [fit onto the camera or Seben Zoom for visual or full disk + camera ... it works - tested a long time ago!].

I also inserted a 2" IR/UV before the PST eyepiece holder - behind the Etalon and also added a that Meade series 4000 #25 RED filter and is getting nice and sharp visually [they are protected by the reflective front PST lens anyway].

Then I fit my Altair 178M and focused just 3mm inwards from visual focus - not bad.

Then I added my 2.2X telephoto lens in front of PST front lens [as in sweiller test] and I easily focused visually by just 7mm back, now trying to focus camera but it has clouded up - I never get to end a session of tests ever with our wonderful weather!

My next attempt should be next Wednesday [day off] around 12-14:00 should be clear after a possible hard-shower [!] - but I will leave telescope up today and hope for a 10 minutes clear enough to be able to focus and possibly take an image ... or rain!

I do have a couple of questions about the cheap Bresser AR-90L-1200 [F/13.3] - yes it has a 1.25" focuser, but I do not see what impact on the VERY bright Sun would do. - https://www.bresseruk.com/review/product/list/id/6223/

1. Do you think Bresser AR-90L-1200 is a decent choice for a PST mod?

2. How much should I cut Bresser AR-90L-1200 to get focus ?
I am asking as I see many just cut around 100-120mm and not the whole 200mm

3. I might get the 75mm ERF [cost less] and inserted internally at correct distance [I have to either calculate or play with a couple of strings or tape measure to find the right position.
Doing the insert is easy, my only problem is what to use as ERF holder, being actually 80mm [75mm ERF opening] ans tube is 90mm, although may be less inwards.
Any ideas? I know the 90mm is easier [being actually 100mm or 105mm wide and make a cap] but its price is ridiculous high [for my small pockets]
I might try to find a kind of nylon strip to wrap around and attach to inserter - it must be thin.

4. ERF type Baader 75mm or Lunt 75mm - the price is the difference for me, but usually Baader is the best one. IS it worth the price difference?


Thank you for all your help, I am getting there and understanding a bit more now. :bow
Mauro


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https://www.youtube.com/@Astronomo_Space

Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by marktownley »

solarchatted wrote: Sun Jul 21, 2019 10:44 am
I also inserted a 2" IR/UV before the PST eyepiece holder - behind the Etalon and also added a that Meade series 4000 #25 RED filter and is getting nice and sharp visually [they are protected by the reflective front PST lens anyway].


I do have a couple of questions about the cheap Bresser AR-90L-1200 [F/13.3] - yes it has a 1.25" focuser, but I do not see what impact on the VERY bright Sun would do. - https://www.bresseruk.com/review/product/list/id/6223/

1. Do you think Bresser AR-90L-1200 is a decent choice for a PST mod?

2. How much should I cut Bresser AR-90L-1200 to get focus ?
I am asking as I see many just cut around 100-120mm and not the whole 200mm

3. I might get the 75mm ERF [cost less] and inserted internally at correct distance [I have to either calculate or play with a couple of strings or tape measure to find the right position.
Doing the insert is easy, my only problem is what to use as ERF holder, being actually 80mm [75mm ERF opening] ans tube is 90mm, although may be less inwards.
Any ideas? I know the 90mm is easier [being actually 100mm or 105mm wide and make a cap] but its price is ridiculous high [for my small pockets]
I might try to find a kind of nylon strip to wrap around and attach to inserter - it must be thin.

4. ERF type Baader 75mm or Lunt 75mm - the price is the difference for me, but usually Baader is the best one. IS it worth the price difference?
The use of the Meade 4000 filter still concerns me. It's an absorptive filter, it will crack at some point!

In the world of solar you pays your money and takes your choice. A decent focuser is key in a PST mod, the mod kit hanging off the back of that 1.25" focuser is likely that it will sag, this tilts the etalon and will cause it to go off band.

You need a f10 scope for a PST mod to work ideally, the 90/1200 is f13.3, it will only complicate things and result in sub optimal performance.

In terms of sub aperture ERFs wrapping the perimeter of the ERF in electrical tape to male up to the correct diameter for an interference fit in the tube would work. A couple of self tapping screws immediately either side of it would act as retainers.

The Lunt ERF is much thinner than the Baader, just means wavefront error is likely to be higher.


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Re: Planning my first PST mod and need some help

Post by solarchatted »

This is my latest PST-SCT v2 - it is better, unfortunately no good weather today!
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SolarChatted
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Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by solarchatted »

[/quote]

The use of the Meade 4000 filter still concerns me. It's an absorptive filter, it will crack at some point!


[/quote]

Thanks for the info ... and regarding the RED filter, I only meant within this mod - i.e. the PST tube is in front of it - the IR/UV + RED is fit on the 35mm extension after the etalon ... as a test and it seemed contrasting well - for the few minutes I had with this weather.

Regarding the AR90/1200 F/13.3, I always thought PST mod was F/10 upwards and not F/10 full stop.


SolarChatted
https://astronomo.space/my-images/the-sun/
https://www.youtube.com/@Astronomo_Space

Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by Merlin66 »

If the donor is faster than f10, the etalon assembly will act as an aperture stop and give an effective f10 system.
If the donor is >f10 then the beam is not affected by the etalon assembly and will still give a system >f10.
Example: an f8 say 100/800mm will become a 80/800mm system; an f12 say 100/1200mm will still be an f12, 100/1200mm system.


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Re: Planning my first PST mod and need some help

Post by AndiesHandyHandies »

Hi

Read this post about PST safety

www.diane-neisius.de/coronado_pst/index_E.html

I got an adapter from the PST front thread to M48 so I can put a 2" Baader 35nm and/or a Belpotic 2" KG3 with UV-IR blocking at the front to make the PST safe. My original PST with the ERF on the front is rusted so RodAstro wants to take the lens apart and polish off the coating so I will need the front filters then.

The problem with 4" F10 telescopes is their size. But a cheap one is good for cutting down.

Another way is to get a cheap F6 and add a Baader 1.25" 1.25x glasspath Barlow in front of the etalon. As there its effectively 200mm in front of the focal point it works as a 1.5x Barlow. F6 x 1.5 = F9. The PST will vignette it to F10. You could space the Barlow a bit further forward with extension tubes, as in my post before to get to F10. Laying out my bits I found I need a M48 to T2 adapter as the extension tubes in front of the PST are 'going the wrong way', handed because of the threads.

Andrew

I have a TS F6.7 I am going to add the Baader Barlow to to get F10. Lighter than my 127mm F7.5 for testing anyway.


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Re: Planning my first PST mod and need some help

Post by solarchatted »

Hi
Thank all for the further info.
I have ordered a Bresser AR90/900 - let's see what happens.

I will need to find exactly how much to cut! Brrrr - no mistakes allowed here !!

Mauro


SolarChatted
https://astronomo.space/my-images/the-sun/
https://www.youtube.com/@Astronomo_Space

Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by solarchatted »

AndiesHandyHandies wrote: Mon Jul 22, 2019 9:07 am
Read this post about PST safety

www.diane-neisius.de/coronado_pst/index_E.html
Yes, I remember that article thanks for link - that was what made me use the 2" 'standard IR/UV in front of Etalon on the SCT mod I have in the meantime and added a std red filter that 'never' heated up when I tested the AR152.

I decided if I have to do a decent solar scope, better use a cheap donor one like AR90/900 and eave AR152 alone [for now anyway] I prefer not to use further lenses.

I am sure a 90mm F/10 + a 75mm right placed ERF will do a good job - I am an amateur not a scientist, although we always aim to better ourselves - we seem to never stop!

;p]

PS when I use it visually, I also add another 1.25" IR/UV filter onto my Seben 8-24mm Zoom - I wonder if we can use a mobile phone camera and a IR/UV app to generally measure danger levels!
Last edited by solarchatted on Mon Jul 22, 2019 3:19 pm, edited 1 time in total.


SolarChatted
https://astronomo.space/my-images/the-sun/
https://www.youtube.com/@Astronomo_Space

Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by solarchatted »

Just curious, but regarding the BF10 [probably for the future], why not try and find just the 10mm BF glass and drill the PST 5mm to 10mm and replace it?

Is that possible? I mean find a BF10 - just the glass?


SolarChatted
https://astronomo.space/my-images/the-sun/
https://www.youtube.com/@Astronomo_Space

Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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Re: Planning my first PST mod and need some help

Post by AndiesHandyHandies »

Hi

The AR90 looks a good choice as available new. I never came across it when looking for a OTA.

I would first use it with the 2" UV-IR placed up the tube where its just under fully illuminated.
The dielectric filters only absorb a bit of energy in the coating. For the space telescope I used for an example a coating absorbs 6% on a mirror. Anti-reflection coatings do absorb more.

Unless you find the telescope seeing is worse than your typical atmospheric seeing at 90mm aperture then a big ERF is a luxury. Daytime seeing will be worse than nighttime. AstroRod says 40x is a popular eyepiece magnification. The eye can resolve 2 arc minutes. So 120 arc seconds / 40 = 3arc seconds which is probably typical daytime seeing.

As I said a D-ERF (external) or a ERF(internal) using the same technology will absorb the same percentage of heat, and its in the same solid angle.

Andrew.

Andrew


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Re: Planning my first PST mod and need some help

Post by solarchatted »

News!
Got the AR90/900mm F/10 Bresser Refractor - everything is plastic but the tube !
Even the focuser is plastic - I mean the whole focuser block held by 3x 8mm Parker screws - that is what you get for just around £. 100

Anyway, dismounted the original plastic focuser and I was left with ~85mm hole and a 90-100g Tuna Fish Tin just fits with 0.5mm spare ...

So, I drilled the main hole 50mm [using 2mm drill bits] then used a Rasp for Metal over the drill to shape it and reasonably forced AOK Etalon to 2" adaptor in and screwed back onto the SCT/PST focuser unit.

The Tuna Tin is sited to make Etalon 18cm inwards - I simply measured from centre of front AR90 lens to back and it just happen to be about 5mm inside the end of the tube [without its original focuser] = LUCK - finally some ...

I will have to do another Tuna Fish Tin but shorter - fit it the other way around - as it touches the Etalon and I cannot push it forward in another 2cm.

Hopefully make it 20cm exact.

I tried it for a few minutes on a ' wobbly ' camera tripod and it seemed to almost be in focus at maximum 25mm out of the SCT focuser - that conforms it needs to be 10-20mm more inward - hence the Tuna Fish Tin modification.

Tomorrow morning or until I am home for a short break [Sunday], I will try telescope properly on EQ6 - more stable - and manually move the focuser in out to see how much more I need - if needed anything.

Once I have the correct distance, I will see to make an adaptor with something sturdier.

Pity I cannot afford a 3d Printer or that would have been an easy solution.

PS still user IR/UV + RED filter - did not heat and also image seems slightly dimmer than the AR152 cut down to 100mm - better telescope lenses I guess.

These are quick tests, I do not see any danger as I have been using it for hours no cracks no t heating at all.

Then the 75mm [or less] ERF - I noticed telescope has a cut don plate to ~ 50mm at about 28.5cm from edge of tube - focuser side - therefore I might only need a 63mm the one used for SCT's - I am guessing here.

That means I can easily slide it on it and lock it with some strong thick black foam forced in - I might fit it over the lens side - if lens side comes off - I am guessing they have glued it on this model !!!

to be continued ...


SolarChatted
https://astronomo.space/my-images/the-sun/
https://www.youtube.com/@Astronomo_Space

Solar Gear:
Bresser AR90/900 + PST mod + SW Auto Focuser ...
Sometime I use Explorer Scientific AR152/988 + Used once only... Altair 2" Solar Wedge (very good indeed)
Will try and do it justice when I can with the help of various filters, Baader 1.25" Solar Continuum 10nm is one.
SW 72ED Pro - fixed 'stock faulty' focuser ... 'I think' !
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