Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 » Mon Feb 24, 2020 3:08 am

BF30 = 30mm
My preference would be the larger Baader, blocks UV, most of the visible and the NIR.


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by AndiesHandyHandies » Mon Feb 24, 2020 9:12 am

Hi,

Large front mounted DERFs let 40%-60% of the spectrum through from a review in Cloudy Nights I saw. Cannot find again and lost a file with a link in. The Baader DERF is the same technology as the 1.25" and 2" 35nm Baader filters. From Astrographs experience a 1.25" will work up to 4" and a 2" up to 6" diameter as an ERF, I use ERF to denote an internal DERF.

Using a laser pointed IR thermometer the optics behind a 1.25" on a Vixen VMC 110mm F10 are not discernable temperature over ambient. The back of the secondary, taken the cover off, is not hot.

The filters need to be at a position where they are fully illuminated and care taken where the reflected focus is.

In the VMC I put the 1.25" Baader after the moved forward PST -200mm collimator lens so the light is reflected out as it came in so no hot spot at all. I put extra aluminium baffles on the secondary and on top of the baffle tube. To mask the un-blackened corrector lenses in the secondary and limit the cone going down the baffle tube to minimise reflections off the inside.

My image is limited by external seeing in practice it appears to me.

Andrew.



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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Rusted » Mon Feb 24, 2020 9:56 am

I have built a new 6" H-alpha telescope after permanently damaging my ZWO ASI120MC.

Despite the internal 90mm D-ERF I was able to burn my hand in the focused beam at the empty focuser. The heat must have damaged my camera even after passing through the etalon, ITF and BF. During video capture my 120MC shows a persistent, translucent mask, identical to solar surface features at the same scale I see on the monitor. I count myself lucky I did not do much visual observing once I caught the imaging bug!

The new OTA has an iStar 150/10 objective. A full aperture 160mm Baader D-ERF is fixed up front. Following helpful advice, given here, I am now protecting my PST etalon [and my ASI174 camera!] with 2" Beloptik KG3 and Baader CCD filters in front of the etalon.

If we ever get any sunshine I shall try to measure the temperature at the focal plane. First with only the D-ERF and objective fitted to the OTA.
Then again, with the two, blocking filters fitted into the empty focuser.


http://fullerscopes.blogspot.dk/

Baader 160mm D-ERF, iStar 150/10 H-alpha, Baader 35nm H-a, Beloptik KG3, PST etalon, Lunt B1200S2, ZWO ASI174.

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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by daslolo » Mon Feb 24, 2020 11:44 am

Rusted wrote:
Mon Feb 24, 2020 9:56 am
Despite the internal 90mm D-ERF I was able to burn my hand in the focused beam at the empty focuser. The heat must have damaged my camera even after passing through the etalon, ITF and BF. During video capture my 120MC shows a persistent, translucent mask, identical to solar surface features at the same scale I see on the monitor. I count myself lucky I did not do much visual observing once I caught the imaging bug!

protecting my PST etalon [and my ASI174 camera!] with 2" Beloptik KG3 and Baader CCD filters in front of the etalon.

If we ever get any sunshine I shall try to measure the temperature at the focal plane. First with only the D-ERF and objective fitted to the OTA.
Then again, with the two, blocking filters fitted into the empty focuser.
You're lucky! I would have burnt my eyeballs because I'm observation only. Do you know how that happened?

Your test will be very useful, and you can get a cheap uv measuring thing on amazon.
If someone can hold a camera while you test that, this'll add to this excellent video: https://www.youtube.com/watch?v=pJ1uqKaisFE


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 » Mon Feb 24, 2020 9:51 pm

The subject of "burning lenses" was raised previously....
Based on the known data I prepared a spreadsheet shows the various effects of a ERF/ etalon/ITF/ blocking filter on the energy transmission.
Solar ignition.zip
(8.16 KiB) Downloaded 116 times
I regularly use my ASI 174 and ASI 1600 on both my PST mod; full D-ERF, PST etalon, BF15 (102/1100) and the SM60/ED 80/ BF15 instruments and have not seen any adverse effect on the cameras......


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 » Mon Feb 24, 2020 11:31 pm

daslolo,
I see you mention 60% transmission for the Baader D-ERF - where did this come from?
From my measurements based on the Baader data I get around 26% .......


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by daslolo » Tue Feb 25, 2020 6:06 am

Merlin66 wrote:
Mon Feb 24, 2020 9:51 pm
Based on the known data I prepared a spreadsheet shows the various effects of a ERF/ etalon/ITF/ blocking filter on the energy transmission.
Solar ignition.zip
Love that spreadsheet, I put it on google sheet for my private use and I'm thinking that the data on that stuff is scatterred far and wide, I could collect it and put it in a google doc for everyone to use and comment on, what do you say?
Merlin66 wrote:
Mon Feb 24, 2020 11:31 pm
I see you mention 60% transmission for the Baader D-ERF - where did this come from?
From my measurements based on the Baader data I get around 26% .......
Found it in one of the many posts I read here. Can you explain your 26% what it means and how you measured?


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 » Tue Feb 25, 2020 6:24 am

The D-ERF transmission curve shows the detail....
The UV (30% of the total solar energy) is suppressed, between 400 and 700nm (another 30% of the total solar energy) it only passes 35nm in Ha, this reduces the energy by >90% ( by >27% of the total, and the low transmission in the NIR brings it down to the 27% I quote.
I’m not at my computer, but can give more detailed calculation.....


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by daslolo » Tue Feb 25, 2020 7:16 am

Merlin66 wrote:
Mon Feb 24, 2020 9:51 pm
Based on the known data I prepared a spreadsheet shows the various effects of a ERF/ etalon/ITF/ blocking filter on the energy transmission.
Solar ignition.zip
I read through this, put it here for easier viewing than having to unzip a file. https://bit.ly/2vYUIP8
What is it about? No filter vs filter viewing through the same f/ scope?


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 » Tue Feb 25, 2020 7:49 am

No, it shows the transmission of the incoming solar energy through scopes...
With an Herschel wedge, with various filters and the PST mod.
You can enter your own data and show the difference between any scope, f ratio and focal length.
The final solar energy intensity is related to aperture, focal ratio and attenuation due to filters.
The example was based on the intensity required to ignite paper....


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Rusted » Tue Feb 25, 2020 9:13 am

The camera problems I have experienced may well be due to the extensive duration of my imaging sessions.
Back in the summer I would often be out in the observatory by 9am.
Then track the sun all day long until it finally disappeared behind the trees at 4pm or even later.
Always using my 6" f/8 internal 90mm D-ERF with no more than PST standard etalon/filtration.

This is pretty extreme by any normal standards of amateur solar imaging and observing.
My assumption that the camera was heat damaged is wide open to conjecture.
The persistent, translucent mask looks just like the solar surface features I see on every imaging session.
I am just being very cautious now. To avoid a repeat with a far more expensive camera.

Here is a live video I captured at the time.
Where I deliberately moved the telescope, with the drives, to show the sun is behind the mask.

https://youtu.be/hHIlU7H2RA0


http://fullerscopes.blogspot.dk/

Baader 160mm D-ERF, iStar 150/10 H-alpha, Baader 35nm H-a, Beloptik KG3, PST etalon, Lunt B1200S2, ZWO ASI174.

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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by AndiesHandyHandies » Mon Apr 06, 2020 9:22 am

Hi

You can put in a 2" Baader 35nm as an internal ERF behind the moved PST Collimator lens, you will not be able to thread it on the front.

The advantage is the reflected energy from the Baader goes back out as an expanding cone the way it came in so no dangerous reflected focus.

It worked for me and only a 1.25" Baader 35nm up to 180mm telescope. I measure 57C on the Collimator/Baader combination. A bit less on the black side of the holder so correct reading.

My Quark is heated to 49C.

Andrew.



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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Rusted » Tue Apr 07, 2020 7:45 am

Hi Andrew,

I am using a 2" Baader 35nm H-a in front of a Beloptik KG3 about 100mm in front of the standard PST etalon group.
Extra insurance for the etalon, filter optics and camera.
A full aperture, 160mm Baader D-ERF sits in front of the iStar 150mm F/10 H-a objective.


http://fullerscopes.blogspot.dk/

Baader 160mm D-ERF, iStar 150/10 H-alpha, Baader 35nm H-a, Beloptik KG3, PST etalon, Lunt B1200S2, ZWO ASI174.

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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by AndiesHandyHandies » Tue Apr 07, 2020 8:43 am

Hi

Plenty of protection there then!

Sometimes it tricky to get filters in a unit you slide up into the focusser.

I am trying to use my New Quark in a even bigger scope (dont tell on me) as it image is dim compared to the PST.

I have added a red dichoric filter after the 'standard' UV/IR which it came with for extra etalon protection. Not as dark red as the Baader.

Unfortunately Daystar, as many others (My TMB diagonal nose has no 48mm thread a real nuisance when my identical manufactured 40mm eyepiece does) did not think to thread the 2" nose piece so I cannot add extenders to put a 2" Baader up before the whole show and in a place where the heat will exit the telescope out of the light path.

I am getting to the thermal limit for a 1.25" blocker I think and thats in haze.

My idea to have the ERF after the PST Collimator does reduce reflection safety issues, eyes and hot spots inside the scope.
You could use a larger diameter collimator of same focal length further up the OTA as well to spread out the heat load.

Cheers. Andrew.



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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Rusted » Tue Apr 07, 2020 11:59 am

There is a 2" filter thread inside my 2" Baader Click-lock fitting where my protective filters sit.
I have the Click-lock fitted into my DIY turned tailpiece/back plate.
The AOC Swiss etalon nosepiece fits into the Click-lock fitting.
BTW Watch out for the tiny, grub screws working loose on the Baader clamp.
My whole filter stack was rocking up and down until I discovered the cause.
Easily fixed with a tiny hex key.

P1410517 rsz 600 txt.jpg
P1410517 rsz 600 txt.jpg (82.82 KiB) Viewed 5278 times


http://fullerscopes.blogspot.dk/

Baader 160mm D-ERF, iStar 150/10 H-alpha, Baader 35nm H-a, Beloptik KG3, PST etalon, Lunt B1200S2, ZWO ASI174.

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