Planning my first PST mod and need some help

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solarchatted
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Planning my first PST mod and need some help

Post by solarchatted » Tue Apr 09, 2019 2:56 pm

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
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solarchatted
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Re: Planning my first PST mod and need some help

Post by solarchatted » Tue Apr 09, 2019 3:00 pm

You can PM me, if you wish ...
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Re: Planning my first PST mod and need some help

Post by solarchatted » Tue Apr 09, 2019 3:33 pm

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.
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Re: Planning my first PST mod and need some help

Post by marktownley » 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.
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Re: Planning my first PST mod and need some help

Post by Merlin66 » Wed Apr 10, 2019 12:49 am

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 » 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.

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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