Dismantling and modification of a PST CaK

Frankenscope? Let's see it!***be advised that NOTHING in this forum has been safety tested and you are reading and using these posts at your own peril. blah, blah, blah... dont mess around with your eyesight when it comes to solar astronomy. Use appropriate filtration at all times...
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Dismantling and modification of a PST CaK

Post by bart1805 » Sat Oct 13, 2018 11:54 am

Here is the story of dismantling a PST CaK. In the end, the plan is to start spring with a doublestacked CaK filter.

1. The original PST CaK

Image20181012_183558_resized_1 by bart moors, on Flickr

2. Problem number 1, destroyed one of the screws, so had to drill it out.

Image20181012_184327_resized_1 by bart moors, on Flickr

3. The inside of the PsT CaK

Image20181013_113749_resized_1 by bart moors, on Flickr

It looks exactly the same as a "normal" PST

Image20181013_113909_resized_1 by bart moors, on Flickr

Two other pictures of the inside of the PST, first one from the front, seconde one from the top (right side points to the frontlens).

Image20181013_121223_resized_1 by bart moors, on Flickr

Image20181013_121239_resized_1 by bart moors, on Flickr

Here you can see the retaining ring that holds the cell the #2 filter is placed in.

Image20181013_113827_resized_1 by bart moors, on Flickr

4. The #2 filter
It is quite easy to release the filter cell, just by turning the retaining ring. Use a screwdriver (gently) and it pops out.

Image20181013_114905_resized_1 by bart moors, on Flickr

Yes it is damaged.

Image20181013_115114_resized_1 by bart moors, on Flickr

And consists of two pieces.

Image20181013_115039_resized_1 by bart moors, on Flickr

5. The front lens
With a lens spanner it is east to pop the front lens out.

Image20181013_114121_resized_1 by bart moors, on Flickr

And here it is, lying on the retainer ring.

Image20181013_115630_resized_1 by bart moors, on Flickr

6. You can see the #1 filter and the retaining ring.

Image20181013_115716_resized_1 by bart moors, on Flickr

Could reach the retaining ring, but could not move it. So that is it for now, winter is still long. Will try again to remove the tube the way it is supposed. But otherwise will drill two holes in it and use a metal rod to twist everything.

If anybody needs other pictures, please let me know, it is all lying around here.

CS! Bart.

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Re: Dismantling and modification of a PST CaK

Post by christian viladrich » Sat Oct 13, 2018 12:15 pm

Thanks a lot Bart !!
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Re: Dismantling and modification of a PST CaK

Post by christian viladrich » Sat Oct 13, 2018 12:21 pm

Just wondering whether you could apply some heat arround filter n1 ? Maybe there is some glue ?
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Re: Dismantling and modification of a PST CaK

Post by bart1805 » Sat Oct 13, 2018 12:25 pm

christian viladrich wrote:
Sat Oct 13, 2018 12:21 pm
Just wondering whether you could apply some heat arround filter n1 ? Maybe there is some glue ?
Yes, that is another possibility, can't see the glue if I look in the tube, but most of the times it is somehow glued. Have got another gold tube of a PST lying around here, will check later if they are the same size. If so, even destroying one of them means I can still rebuild the CaK to it's original state.

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Re: Dismantling and modification of a PST CaK

Post by bart1805 » Sat Oct 13, 2018 2:47 pm

I know Apollo, and I have tried it with a strap wrench. Have freed 2 PST etalons with it without major problems, but this one hates to be liberated.
Here is the last light of the PST CaK. Could not get into focus, so removed the upper part of the eyepiece holder. Asi290mm with a single Baader CaK filter.

ImageSun_10121243161_PSTCaK_BaaderCaKsingle by bart moors, on Flickr


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Re: Dismantling and modification of a PST CaK

Post by christian viladrich » Sat Oct 13, 2018 4:42 pm

So, finally there are two filters :
- Number 2 at the rear. Actually it consists in two parts (glued ?).
- Number one at the front (behind the lens ?), this one is a GG395 according to the information given by Apollo.
Is this correct ?
No filter at the front of the eyepice ?
BTW, the lens seems to be a doublet ?
Christian
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Re: Dismantling and modification of a PST CaK

Post by marktownley » Sat Oct 13, 2018 4:50 pm

Yes, the lens is a doublet Christian
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Re: Dismantling and modification of a PST CaK

Post by bart1805 » Sun Oct 14, 2018 1:43 pm

Free at last!
Good day today. First tried to dismantle the Lunt B600 diagonal.
With a lens spanner it is really easy to twist the retaining ring of the BF:

Image20181014_141955_resized by bart moors, on Flickr

And there lies the square Lunt Blocking filter:

Image20181014_142039_resized by bart moors, on Flickr

Loosen the two screws on the diagonal and torch it a bit. Then the cell comes out, here you see it upside down. Look at the amount of glue that was used.

Image20181014_153708_resized by bart moors, on Flickr

It is just glued on the diagonal, the two screws are extra. So no thread:

Image20181014_152027_resized by bart moors, on Flickr

And after this used the Ruler-method to twist the retaining ring of the #1 PST CaK filter. If you have a good grip, it is really easy. That is it for today: a free Coronado and a free Lunt CaK filter. The #1 filter was lightly glued to the retaining ring, you can see the residu.

Image20181014_151818_resized by bart moors, on Flickr

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Re: Dismantling and modification of a PST CaK

Post by bart1805 » Sun Oct 14, 2018 5:52 pm

Here you can see that the Lunt filter consists of two pieces:

Image20181014_190801_resized by bart moors, on Flickr

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Re: Dismantling and modification of a PST CaK

Post by bart1805 » Sun Oct 14, 2018 9:46 pm

250 dollar for that 40 mm objective lens? That is quite a lot, did not know that. Have two of them, so maybe I will make a UV optimised bino with them. (-;
I found it typical that the #1 filter is glued to the retaining ring where the #2 filter is not. Any particular reason you know of?

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Re: Dismantling and modification of a PST CaK

Post by bart1805 » Sun Oct 21, 2018 10:15 am

Even after applying some heat on the blue collar of the PST CaK I could not remove it from the black box. So removed the lens and put it in a gold tube of a H-alpha PST. The difference in coatings is clearly visible. On the left the CaK objective.

Image20181021_114011_resized by bart moors, on Flickr

So now I have got clouds and and ready to go 40mm CaK telescope. From left to right after the gold tube:
- Adapter made by AOK
- JMI EV focuser
- Baader 2 inch clicklock
- 1,25 inch Skybender
- ASI 290mm

Image20181021_120317_resized by bart moors, on Flickr

Image20181021_120334_resized by bart moors, on Flickr

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Re: Dismantling and modification of a PST CaK

Post by marktownley » Mon Oct 22, 2018 6:02 am

I replaced the objective in my sm40 for one from a Cak PST too 😉
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Re: Dismantling and modification of a PST CaK

Post by bart1805 » Thu Oct 25, 2018 7:36 pm

TheSkyBurner wrote:
Thu Oct 25, 2018 6:18 am
so i figured out the best way to remove a locked pst tube.

You need to find a pipe vice.
Yep, that looks good. But with the ruler method it is not really necessary to remove the tube. But would be handy for a regular PST. Thanks!

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Re: Dismantling and modification of a PST CaK

Post by bart1805 » Sat Nov 03, 2018 3:42 pm

The second PST CaK will be here in about two weeks I think. Thanks to Apollo and Marty I found the right filter cell for the 25mm PST #1 filter.
Here is how it looks now:

ImageCaKfilter_annotated by bart moors, on Flickr

The Lunt B600 can be replaced by the second PST #1 filter. And will have to experiment with one or two of the single Baader CaK filters. Etc.

And the PST CaK mod:

Image40mm_annotated by bart moors, on Flickr

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Re: Dismantling and modification of a PST CaK

Post by marktownley » Sat Nov 03, 2018 3:46 pm

Nice creations Bart!
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Re: Dismantling and modification of a PST CaK

Post by bart1805 » Sat Nov 03, 2018 4:19 pm

marktownley wrote:
Sat Nov 03, 2018 3:46 pm
Nice creations Bart!
Thanks Mark. Tomorrow, if the weather permits, will test it with the Bresser 127mm f/10.

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Re: Dismantling and modification of a PST CaK

Post by bart1805 » Sat Nov 03, 2018 8:27 pm

TheSkyBurner wrote:
Sat Nov 03, 2018 7:27 pm
You can totally eliminate that baader planetarium K-filter (i would resell it), put the pst filter in the tilter instead so you can take blue wing images with a couple twists..
Maybe I will Apollo, but not before trying out all the different combinations I can come up with.

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Re: Dismantling and modification of a PST CaK

Post by bart1805 » Sun Nov 04, 2018 10:47 pm

A lot of high clouds today and the sun is quite low here in the Netherlands. But at least I could give it a try. Used a Bresser Messier 127mm f/1200 mm stopped down to 10 cm.
Set up used was Baader Blue / Single Baader CaK / PST CaK #1 / Baader Blue / LuntB600.
With just the PST #1 filter (so no Lunt) the image was better than with just the B600 (so no #1 PST). Image was best when used both the Lunt filter and the PST #1 filter. Sun was a bit boring, and you can see the vignetting caused by the small Lunt Filter. Camera used was the ASI290mm.

ImageSun_123501_alles43063_PS by bart moors, on Flickr

Still a lot of experimenting and trial and error to be done in the near future, but at least it has started!

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Re: Dismantling and modification of a PST CaK

Post by marktownley » Mon Nov 05, 2018 7:01 am

Good result. That 290 is on my shopping list for next year.
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Re: Dismantling and modification of a PST CaK

Post by bart1805 » Tue Nov 06, 2018 8:53 pm

Thanks Mark, I really like the 290.

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Re: Dismantling and modification of a PST CaK

Post by bart1805 » Fri Nov 16, 2018 10:14 am

Received the second PST CaK today. Lower number: 50095. And I could screw the gold tube by hand of the blue ring. No force needed at all. Filter cell also unscrewed by hand, no force needed. Less glue was used to attach the filter to the retaining ring. So in about 3 minutes I had a second PST CaK #1 filter in a new cell. Doublestacking time!

Image20181116_104544_resized by bart moors, on Flickr

Image20181116_110410_resized by bart moors, on Flickr

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Re: Dismantling and modification of a PST CaK

Post by marktownley » Sat Nov 17, 2018 12:46 pm

It is good when the PSTs just unscrew. I've had a few that have been able to just unscrew, but also a few that were stuck fast.
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Re: Dismantling and modification of a PST CaK

Post by bart1805 » Sun Nov 18, 2018 4:32 pm

TheSkyBurner wrote:
Sat Nov 03, 2018 7:27 pm
You can totally eliminate that baader planetarium K-filter (i would resell it), put the pst filter in the tilter instead so you can take blue wing images with a couple twists..
Could experiment this morning for about half an hour. The altitude of the sun was 15 degrees. And I really needed the Baader K-line, otherwise the image was washed out, looked a bit like continuum without the K-line. Maybe you can do without the Baader if you use a Chroma filter.

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Re: Dismantling and modification of a PST CaK

Post by bart1805 » Sat Dec 01, 2018 2:46 pm

Ready to go!
Found a secondhand Celestron 102 ED (f/9). Changed the original focuser for a Baader Steeltrack version.
Mounted inside are:
2 inch Baader Blue CCD
2 inch Beloptik UV/IRcut on KG3
Baader CaK filter (mounted the two original filters in two filter cells.
PST #1 filter on nosepiece of Skybender
PST #1 filter inside Skybender.

Image20181201_153405_resized by bart moors, on Flickr

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