How can I modify my CaK PST?

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eroel
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How can I modify my CaK PST?

Post by eroel » Mon Jan 19, 2015 2:39 pm

Hello:
Well, I have been thinking of using a 102mm f/9 Meade refractor for CaK imaging. (no observing, because I can not even see the solar disk through the stock PST) :(
After reading Mark´s articles and photos where he shows all the parts that conform a stock PST, I proceeded to take it apart.
Everything was easy, except taking off the blue collar from the golden tube, though I used a steel ruler and a lens spanner to take all the filters out first.
After that, I just used a Butane torch to just heat a little bit the blue collar, and then I unscrewed it easely by hand, I could have done it with the filters on, because it just needed a bit of heat on the collar so it would expand a bit, and loosen the glue or whatever they put on.

Now to the parts I already have:
1- Baader 1.25" K line filter.
2- Baader 1.25" Venus filter.
3- IDAS 1.25" blocker (the one Jen Winters recommends as a CaK ERF).
4- Lunt 1.25" wedge without the ND filter.(took it out)
5- SAFIX unit if needed.

So I think that I have enough parts to make the mod, but don´t know exactly where to put all the ingredients, including which side of them has to face the objective of the scope.
For example, the thick 1" filter (#2) that goes on the back of the thin 1" yellowish filter (#1), has a > mark, I suppose that the open part goes to the objective, isn´t it?
So as you can see, I need to know which way to install each filter that came out of the PST.

BTW, I know that I am doing all this at my own risk, though i had been for years a telescope maker and have made and refigured many optical surfaces, from 1" to 24" in diameter, flats, spheres, paraboloids, and complete systems like Maksutov, R.C., Schmidt camera, Wright, Classical Cassegrain, Gregorian, Dall Kirkham, Newtonian, etc, so I know how to handle and clean optics and know that this modification takes off all warranties.

Well, I am open to hear what to do with what I have.

Thanks you all,

Eric.

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Re: How can I modify my CaK PST?

Post by swisswalter » Mon Jan 19, 2015 8:09 pm

Hi Eric

fantastic, well come to the blue side

I work the following way, seen from the objective


2" UV/IR cut from Beloptic on KG3, 1 LUNT hot mirror from the CaK wedge, PST filter #1 (the thin one) , Lunt CaK filterstack from the B1200, Baader K-line filter, 1,25" UV/IR cut from Beloptik on KG3 or a TS IR cut filter

Have fun in the sun
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Re: How can I modify my CaK PST?

Post by eroel » Mon Jan 19, 2015 8:59 pm

Walter:
You have a Lunt CaK filter, I just have the CaK filter that comes with the PST, so what can I do?
Best wishes,
Eric.

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Re: How can I modify my CaK PST?

Post by marktownley » Mon Jan 19, 2015 9:07 pm

Really easy Eric! Lunt wedge with any ND filters, then Baader K-line, then the magic yellow filter from the CaK PST, then your CCd camera. You'll be ready to go then ;)
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Re: How can I modify my CaK PST?

Post by Valery » Mon Jan 19, 2015 9:15 pm

eroel wrote:Walter:
You have a Lunt CaK filter, I just have the CaK filter that comes with the PST, so what can I do?
Best wishes,
Eric.
Hi Eric,

If you like, I can describe my system.

100mm F=1000mm objective -> 2" ERF Hoya 80A filter -> CaK PST #2 -> CaK PST #1 -> SAFIX with F/10 barrel -> camera or a 1,5x, 2x Barlow before the camera.

Also, for better contrast (a little improvement) I use an Edmund Optics 393nm hard coated filter on the camera nosepiece.

Works great and I have a plenty of contrast. If the objective is around neutral spherical aberration at a green light (symmetrical star test on both sides of focus),
then I use -2,5 to -3 on the SAFIX Barrel. This makes images EXTREMELY sharp when the seeing is OK or better.
If I do not need high resolution, I don't use SAFIX.

Hope this helps.


Valery.
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

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Re: How can I modify my CaK PST?

Post by eroel » Mon Jan 19, 2015 11:17 pm

Walter, Mark and Valery:
Thanks, now I have several ways of going on, but have some questions:
1-Which one is the PST magic yellow filter, #1 or #2.
2- Which way should it face the objective.
3- I will install the SAFIX in the lens train.
Valery, the SAFIX really works wonders, I am putting 2 images, 1 taken without SAFIX and 1 taken with it, they were taken with the Meade 102mm f/9 refractor and processed equally.
Thanks,
Eric.
Luna-1 enero 2015 -M-1bc.jpg
Luna-1 enero 2015 -M-Safix-1bc.jpg

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Re: How can I modify my CaK PST?

Post by Valery » Tue Jan 20, 2015 3:32 am

eroel wrote: 1-Which one is the PST magic yellow filter, #1 or #2.
2- Which way should it face the objective.
1. When you disassemble the CaK PST, the first filter counting from the objective is the yellowing filter #1 - the main Ca K filter.

2. Better to not disassemble this front cell with two filters ( first is #1 yellowing and #2 mirror like one) and use it vise versa - the filter #2 (mirror like) in front, faced to the objective and then this #2 filter will work as a mini-ERF filter too. I'd keep the main filter at as safer position as possible. It is the best CaK filter on the market today.


Note very important thing, Eric. The distance between the cell with two first filters and the focal point must be not less than 150mm and not more than 180mm if you do use a 100mm F=1000mm refractor or 90mm F=900-1000mm.

If you will use only two filters (no additional K-line filter or Edmund 393nm ) then better to unscrew the CaK #1 yellowing filter and use it in a front of camera at the camera nosepiece. The filter #2 should be used in it's original cell - it has there a tilt and so, you will have no issues with reflections.

I machined the interface between the cell of two first filters of the CaK PST and the standard 2"-1.25" adapter. Now my CaK train is ready to be used with
any F/10 telescope with 2" output.

Hope this helps.


Valery.
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

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Re: How can I modify my CaK PST?

Post by swisswalter » Tue Jan 20, 2015 5:19 am

Hi Eric

crackling moon shots. The way Mark described is the easiest. I would additionally use an UV/IR cut from Beloptik on the nose of the CCD or a TS IR block. ND filter only as needed. I work with exposures around 1 - 4 ms
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

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Re: How can I modify my CaK PST?

Post by marktownley » Tue Jan 20, 2015 6:48 am

Valery wrote: 2. Better to not disassemble this front cell with two filters ( first is #1 yellowing and #2 mirror like one) and use it vise versa - the filter #2 (mirror like) in front, faced to the objective and then this #2 filter will work as a mini-ERF filter too. I'd keep the main filter at as safer position as possible. It is the best CaK filter on the market today.
I disagree here Valery, filter #2 (the mirrored filter) is a silvered filter that has the same purpose of an ITF in a coronado blocking filter - blocking out to >2500nm, however as a result of this it is prone to 'rusting' that progressive failing where moisture ingress from the edges of the filter causes a gradual cloudiness and loss of contrast in the image. Both my PST #2 filters were rusted, I think there's a picture of it in one of the CaK PST threads somewhere on here. However, if you use a Baader, which is a hard coated filter this 'rusting' does not occur, and you also get more light through. The PST #1 filter (yellowy looking one) is a hard coated filter, so fortunately won't rust Eric, you will be pleased to know!

However, as your images show Valery you are getting excellent results, and the old motto, 'if it's not broke then don't fix it' certainly applies, however I would urge you to look and see if your PST #2 are suffering rusting...

I have to say Eric, your image comparison with the SAFIX shows startling results, unfortunately myself and Walter could not get it to work like this at all when we tried it...
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Re: How can I modify my CaK PST?

Post by Valery » Tue Jan 20, 2015 11:10 am

marktownley wrote:
However, as your images show Valery you are getting excellent results, and the old motto, 'if it's not broke then don't fix it' certainly applies, however I would urge you to look and see if your PST #2 are suffering rusting...

I have to say Eric, your image comparison with the SAFIX shows startling results, unfortunately myself and Walter could not get it to work like this at all when we tried it...
Hi Mark,

1. My filter #2 is indeed rusted. I tried both combinations: 2" Hoya 80A + PST #1 + PST #2 + Camera and 2" Hoya 80A + PST #1 + Edmund 393nm + Camera
and I saw no difference on images. Identical to my eyes. The only difference is the exposure time - longer with PST #2.
However the highest contrast (especially for prominences) I can reach with PST #2 + PST#1 + Edmund 393nm.
I plan to buy a second PST #1 in near future.

2. About the SAFIX. You need a telescope which has enough back focal distance. To see how the SAFIX changes the SA in a telescope,
take a refractor with about F/7-8, remove the diagonal if it was installed and use F/7-8 SAFIX' barrel. Place a short focus eyepiece in this barrel.
Eyepiece which give 1,5D to 2Dmm magnification.
Point the telescope on a 1-2 magnitude star, install the 0 on the SAFIX scale. See the out of focus star images with defocusing of 3-4 rings.
Do this before and after focus and see the difference. You will sure see a huge difference.

The same will be with images at 393nm. In any objective (except TAK TOA130-150) the SA at 393nm is 0.5 - 2 wave overcorrection (depends of objective D and F/D). So, to compensate this overcorrection which is + , one need to use SAFIX at it's (-) scale part. For my 100mm F/10 achromat I use -2.5 to -3
and the images are very sharp vs soft images with no SAFIX. This is very well seen at large scale. If you doing imaging at low scale - FD or half disk, SAFIX will not improve much.

May be your and Walter seeing is so poor, that there is no real difference. I saw only one Walter's really high resolution CaK image through his 5" or 6" refractor and DayStar 5A filter. All other images from him or you I saw, were low scale - I don't know the reason that only low scale images from you both.

Please, to that SAFIX test on the star and let me know if the SAFIX works.


Valery.
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

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Re: How can I modify my CaK PST?

Post by eroel » Tue Jan 20, 2015 4:11 pm

Walter, Mark and Valery:
A few days ago I tried the SAFIX on the Solarmax 90, I had to use the straight through BF-30, because with the SAFIX you get focus (with an eyepiece) all the way down of the focuser draw tube (Moonlite), anyway I had a chance to try it visually and it is startling to find out that when you put the SAFIX on "0" and focus the image that looks nice and sharp, and then when you move the helical adjustment a one mark or two and the focus just snaps again and gives a view like if you are using another scope, a very gratifying experience. Unfortunately I could not get the camera to focus, but I will try it with a Barlow.
Then I tried it on the Stellarvue 102mm, f/7 and did not find any change with SAFIX, looks like it just works wonders on scopes that suffer from SA.

As for the CaK modifications, I will start experimenting with the various methods explained, first using the setup with the Lunt wedge, then Valery´s setup with the SAFIX if possible.
I did not know that the cell that carries the PST filters #1 and #2, has a tilt for the second filter, so I will try to find out what tilt it is, so to make a new and smaller cell if needed.
Thank you Walter, Mark and Valery for the precious help, now it is up to me, and will post my experiences doing them.
Regards,
Eric.

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Re: How can I modify my CaK PST?

Post by Valery » Tue Jan 20, 2015 7:42 pm

eroel wrote: I did not know that the cell that carries the PST filters #1 and #2, has a tilt for the second filter,
Eric.
Eric,

When you unscrew the filter in the front of CaK PST black box, these two filters front one (#1 yellowing filter) and back one (#2 mirror-like filter) - they both are
in a black cell. Back filter has a small tilt - so, no reflections overlap in the focus.

Valery.
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Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

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Re: How can I modify my CaK PST?

Post by eroel » Tue Jan 20, 2015 8:00 pm

Valery:
Understood, it is important and I will measure the tilt, just to know.
Question, which side of the #1 filter of the PST faces the objective?
Is there an easy way to know which side has to face the objective?
Regards,
Eric.

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Re: How can I modify my CaK PST?

Post by marktownley » Tue Jan 20, 2015 11:16 pm

eroel wrote: Question, which side of the #1 filter of the PST faces the objective?
Is there an easy way to know which side has to face the objective?
Regards,
Eric.
In my experience this does not matter.
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Re: How can I modify my CaK PST?

Post by marktownley » Tue Jan 20, 2015 11:19 pm

Valery wrote:My filter #2 is indeed rusted. I tried both combinations: 2" Hoya 80A + PST #1 + PST #2 + Camera and 2" Hoya 80A + PST #1 + Edmund 393nm + Camera
and I saw no difference on images. Identical to my eyes. The only difference is the exposure time - longer with PST #2.
However the highest contrast (especially for prominences) I can reach with PST #2 + PST#1 + Edmund 393nm.
The reason for the higher contrast is because of the increase in out of band blocking the additional filter provides.
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Re: How can I modify my CaK PST?

Post by swisswalter » Tue Jan 20, 2015 11:25 pm

Hi Eric

lately I tried to find out wether there is a difference using side A or B on the CaK PST #1 but I did not notice any difference at all. I guess there isn't one at all
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

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Re: How can I modify my CaK PST?

Post by eroel » Wed Feb 25, 2015 12:40 am

Hi:
Finally I did make my PST modification and it works, probably i will have to tweek some things and try other filters, so to get the best result possible.

1) I took out the PST CaK module where filters #1 and #2 are housed.

2) Made an aluminium housing 100mm long and with a 2" external diameter, here goes the CaK module with the threads looking out, the rest is kept inside the tube by 3 setscrews.

3) I also made a cap that screws into the module threads and in this cap, there is a hole with threads that receives a 1.25" filter, here I use the iDAS UIBAR as an UV/IR blocker.

4) The aluminum tube receives on the other side any accessory of 1.25" diameter (eyepiece, camera nose, etc.), here I put the camera with the Baader K-line filter on its nose, and thats it.

I plan to try my Baader Venus filter to find out if it is better than the K-line, and also I think of getting a 2" IDAS UIBAR filter, so I will make a cap that can receive this bigger filter.

I will keep commenting my experiences with this CaK module that I will use with an old 102mm f/9 Meade achromat as also with the SAFIX.

If someone wants to ask something concerning the modification, please feel free to ask, meanwhile the photos are self explanatory.
(included is a CaK image taken with a 0.5X reducer at the normal distance from the chip, so to get a FD.)

Regards,

Eric.
CaK-2.jpg
CaK-2.jpg (290.56 KiB) Viewed 1865 times
CaK-3.jpg
CaK-3.jpg (270.68 KiB) Viewed 1865 times
CaK-4.jpg
CaK-4.jpg (306.7 KiB) Viewed 1865 times
Módulo CaK.jpg
Módulo CaK.jpg (196.63 KiB) Viewed 1823 times
Sol del 23 de febrero 2015 -M-CaK-1an.jpg
Last edited by eroel on Thu Feb 26, 2015 2:29 pm, edited 1 time in total.

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Re: How can I modify my CaK PST?

Post by swisswalter » Wed Feb 25, 2015 5:22 am

Hi Eric

congratulations, a cool CaK wedge and a perfect disk
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Re: How can I modify my CaK PST?

Post by marktownley » Wed Feb 25, 2015 6:44 am

Excellent mod there Eric, be interesting to hear how you get on with the Baader Venus filter, keep us updated please :)
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