My PST CaK mod.

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Re: My PST CaK mod.

Post by swisswalter »

Hi Valery

I'll give it a go and will Report. #1+1/2 K-line will be much too bright I will have to dim it down, mabe with a ND3 after the hot mirror


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Re: My PST CaK mod.

Post by Valery »

swisswalter wrote:Hi Valery

I'll give it a go and will Report. #1+1/2 K-line will be much too bright I will have to dim it down, mabe with a ND3 after the hot mirror
Thanks in advance, Walter.

Do you have ND filters or do you have Hershel prism?

BTW. I do plan to use #1+EO 394nm with ERF filter like Schott BG12.


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Re: My PST CaK mod.

Post by Valery »

To be honest, I think that I am a bit exaggerated the problem. Edmund Optics warranted that all wave lengths out of 10nm bandpass are attenuated with optical density OD>4. In fact the OD is about 5 with very few narrow peaks reached OD4. OD4 means light attenuation in 10.000x !
Even if the CaK PST filter #1 has only 10% transmission at 393,4nm, then S/N will be at least 1000. And this is only for these few peaks. For all other wave lengths the ratio will be about 10.000x.
If I will imaging with 8 bit, then I will not see the filter's leakage at all. Even imaging with 16 bit (really expanded from 12 to 16 bit) I will see only a trace of this leakage.


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Re: My PST CaK mod.

Post by swisswalter »

Hi Valery

thank you for your question. I have both, ND filters and Herschel wedges. #1+ 1/2 K-line works not, some sort of WL Image. #1+#2+1/2 K-line works very fine. Pics will follow


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Re: My PST CaK mod.

Post by Valery »

swisswalter wrote:Hi Valery

thank you for your question. I have both, ND filters and Herschel wedges. #1+ 1/2 K-line works not, some sort of WL Image. #1+#2+1/2 K-line works very fine. Pics will follow
If you still at the telescope, can you add #1 + K-line?

Can you, please, give all information about equipment, exposures, frames stacked etc.

Thanks,

Valery.
Last edited by Valery on Sat Jun 07, 2014 2:48 pm, edited 1 time in total.


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Re: My PST CaK mod.

Post by swisswalter »

Hi Valery

I will as far as I can. There are waiting over 80 avis to be stacked and post proprocessed ;)


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Re: My PST CaK mod.

Post by Valery »

swisswalter wrote:Hi Valery

I will as far as I can. There are waiting over 80 avis to be stacked and post proprocessed ;)
A lot of sunny weather in Switzerland?

Please, add #1 + K-line too! This will give a full picture of how all these filters work.


Valery


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Re: My PST CaK mod.

Post by swisswalter »

Hi Valery

thank you very much. I will for sure. But there is nothing new Mark and I did not do a year ago


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Re: My PST CaK mod.

Post by Valery »

Today the mechanical machinist gave me all necessary parts to make my first CaK telescope work. This is a 100mm F=1000mm Bresser achromat.
The train will be as follow:

Objective > internal 50mm ERF (two 80A filters) > #2 PST filter > CaK PST #1 filter > Edmund Optics 394nm filter

In a two weeks I will install front mounted EDF filter which blocks all the radiation from 480 to 2000nm
and has steep ball-like curve and 75% transmission at 394nm.

Two 80A filters reject about 80% of unwanted energy and finally the energy density at the PST filters will be about the same as in native CaK PST scope.

Hope, that tomorrow will be a good blue sky like it was today during my Ha hunting for the Sun.


Valery.


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Re: My PST CaK mod.

Post by Bob Yoesle »

Hi Valery,

My CaK system is very similar: D100mm F900mm Orion (Skywatcher) ED Objective > internal 50mm ERF (Baader Blue CCD filter) > #2 PST filter > CaK PST #1 filter > Baader CaK filter.

Here are some of my better results:
4-9-11 CaK Full Disk jpg SM.jpg
4-9-11 CaK Full Disk jpg SM.jpg (92.58 KiB) Viewed 5122 times
CaK enhanced flsclr2 jpg sm.jpg
CaK enhanced flsclr2 jpg sm.jpg (132.12 KiB) Viewed 5122 times
R_155237 jpg SM.jpg
R_155237 jpg SM.jpg (178.45 KiB) Viewed 5122 times
R_170645 crp sm.jpg
R_170645 crp sm.jpg (191.89 KiB) Viewed 5122 times
Bob


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Re: My PST CaK mod.

Post by swisswalter »

Hi Bob

very fine results indeed


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Re: My PST CaK mod.

Post by marktownley »

Top shots there Bob!


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Re: My PST CaK mod.

Post by Bob Yoesle »

Thanks Walter and Mark; not up their with the work of Luca and Harald though -- need more aperture and better seeing for that. ;)

Best wishes,

Bob


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Re: My PST CaK mod.

Post by Valery »

Hi Bob,

Thanks for your nice pictures. Today I finalized my CaK scope #1. If tomorrow will be a clear day, I hope to image sun in CaK at 1m and 2,3m focal length.
Telescope now work fine, no astigmatism just not the best correction at 393nm.

My next CaK telescope will be 150mm refractor or C11.


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Re: My PST CaK mod.

Post by mdwmark »

I just have minute, K-line blockers (filters) have trouble with leaks in the green. You sometimes get a mismatch in the layers and you get a narrow bandpass that is not blocked by the ITF. Most of the time it's small and sometimes you can use filter glass to cut it out. But I have sent back blockers where the filter glass didn't work. That may be where the turquoise color is coming from.
Mark W.


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Re: My PST CaK mod.

Post by Valery »

mdwmark wrote:I just have minute, K-line blockers (filters) have trouble with leaks in the green. You sometimes get a mismatch in the layers and you get a narrow bandpass that is not blocked by the ITF. Most of the time it's small and sometimes you can use filter glass to cut it out. But I have sent back blockers where the filter glass didn't work. That may be where the turquoise color is coming from.
Mark W.
Mark,

Thanks for this info. But do you mean K-line blockers in general (all blockers for this K-line) or do you mean Baader K-line filters?

As far as I know, five Baader K-line filters work fine for Luca, Andreas Murner, Max Usatov, Walter K. and Mark T. and in this same time my Edmund Optics 394nm has a leak at the green and longer which I see as pale sand color. However, Baader K-line consists two parts (identical ? ). My EO 394nm is a single and it has filtration of other wave lengths at about OD=4-5. The 1/2 of the Baader K-line filter has about the same leak as my EO single. may I suspect that if I have two EO 394nm double staked, I will have other wave lengths filtration on the level OD 8-10 and in such see only the violet which is about 0.9 transmission is a single filter and will be about 0.81 in double stack?

Valery.


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Re: My PST CaK mod.

Post by Valery »

Finally, June 14 and 15, 2014 my Ca-K telescope was tested and finally adjusted. Now it's train is as follow:

100mm F/10 achromatic objective > internal ERF (double 80A filters by B&W) > 394nm 10nm block filter by Edmund Optics > CaK PST filter #1 (yellowing one) > flip mirror system by Vixen > PGR Flea3 GigE mono camera with ICX445 chip.

First and second light of this scope are here:

http://solarchat.natca.net/viewtopic.php?f=4&t=11904
http://solarchat.natca.net/viewtopic.php?f=4&t=11894


Many thanks to Bob Yoesly, Mark Wagner, Mark Tawnley, Walter Kohch and all others who helped me with advices and discussions.
Without your friendly help, this project will not be finished or even was not started at all.

Valery.


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Re: My PST CaK mod.

Post by marktownley »

It's great news Valery! It's what this forum is all about. Now all you have to do is double stack it ;)


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Re: My PST CaK mod.

Post by Valery »

marktownley wrote:It's great news Valery! It's what this forum is all about. Now all you have to do is double stack it ;)
No no! Not only the DS! I also need to increase the apertre at least to 6" and then to even larger. Harald's Paleske CaK images inspire me on growth of the aperture.


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Re: My PST CaK mod.

Post by marktownley »

I've bought some of the UV polarising material as described by Mark Wagner. I will report back on how I get on with it :)


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Re: My PST CaK mod.

Post by swisswalter »

Hi Valery

wonderful progress


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Re: My PST CaK mod.

Post by Valery »

marktownley wrote:I've bought some of the UV polarising material as described by Mark Wagner. I will report back on how I get on with it :)
What will you use them for?

Valery.


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Re: My PST CaK mod.

Post by marktownley »

Valery wrote:
marktownley wrote:I've bought some of the UV polarising material as described by Mark Wagner. I will report back on how I get on with it :)
What will you use them for?

Valery.
Suppressing the reflections / ghosts which will, I am sure, have a positive effect on contrast.


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Re: My PST CaK mod.

Post by mdwmark »

I'm back, The leak in the green is just something I came across over the years. They where with 1nm blockers blocked to the far IR for etalons. The little bandpass in the green where not bright but they where narrow. The main bandpass would be much brighter, so you would loose only a little contrast. But it did change the back ground color. But for my jobs I couldn't have any others but the main bandpass even if it didn't mater.
Mark W.


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Re: My PST CaK mod.

Post by Bob Yoesle »

Hi Mark,

Would you mind explaining a bit about the use of wave plates and polarizers to get rid of reflections, and why to use a circular vs. linear polarizer, and a quarter vs. a half wave-plate is utilized? The Wikipedia article -- http://en.wikipedia.org/wiki/Polarizer -- is a little unclear to me at this point. My limited understanding so far is that the wave-plate "retards" or separates the polarization modes, and a polarizer can then better eliminate one of them - one of which is the reflection(s)...?

Thanks,

Bob


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Re: My PST CaK mod.

Post by mdwmark »

Hi Bob,
I looked up that wikipedia page and I could see why you were a little unclear.
I have another site WWW.ray-optical.com this page belongs to Ray Williamson Consulting. On the page you will find Polarization Optics Tutorial. I think he does a better job explaining wave plates and polarization.
For what we want to do is get rid of secondary reflections. So we really have a broad range of 1/4 wave plates we can use.
If we start with unpolarized light and go through a linear polarizer. We get the standard( depending which school you went to P,S fast, slow, I,O ) two axis of light 90 deg apart.
Next
What is a 1/4 wave plate.
First they are usually not a 1/4 wave thick of the wavelength. They will be a multiple of the 1/4 wave or 3/4 wave to make them thick enough to work with.
The 1/4 wave plate rotates the wave 90 deg( let say counter clock wise). To keep it simple let say we are looking from the side. As the wave move forward. It would look like a the threads of a screw always rotating counter clock wise. If you looked from the end then it would look like it was going in a circle. Now when it hits a mirror it reflects back clock wise and when it get back to the 1/4 wave plate it is blocked because it is now in the wrong direction. So It stops the reflection from hitting the first mirror and reflecting back again.

The standard circulars Polaroids that 3M made, the 1/4 wave plate was design for around 560nm ( but depending how it was stretched it could be thicker or thinner, which means different wavelengths) . But they usually worked from 420nm-700nm for cutting out reflection. They came in gray, amber, red. The only difference was the color of the gel.

What we need is a UV circular polaroid. So it works the same. We placed the UV linear Polaroid axis on a piece of graph paper in the X axis and Y axis. Now the 1/4 wave plate will have its axis marked also. Now we place them 45deg from the X,Y axis. So we have a cross at 90 deg and another one at 45deg. The 1/4 wave plate will be on the back side.

Now come the practical problem. It would be best if this was all greased or laminated together with AR's on the outside windows.
I though about putting one together but I didn't have any AR's windows ( one sided) coated for 393nm. The least expensive AR would be a 1/4 wave of MGF2 at 393.4nm. It wouldn't be very broad band but it would work OK for that small range and we only care about around K-line(it would still be working at the H-line).

There is nothing new about this approach. Spectra Lab presented a paper in 1968 showing the difference between tilting and using circular Polaroids for reflection off two mirrored surfaces. They where using this approach back then with there own filters.
If you look at the ISOON diagram you will find a circular polariod between the etalons on that system.
Mark W.


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Re: My PST CaK mod.

Post by swisswalter »

Hi Mark

thank you very much for the wealth of information


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Re: My PST CaK mod.

Post by marktownley »

Thanks for all this info Mark, I need to do a lot of reading to get my head around what it's all on about!

In the meantime I bought a linear UV polariser; placing it between the 2 K-line elements and rotating the polariser relative to the elements has the effect of darkening the sky glow (which is a result of an out of focus ghost). I just haven't had clear skies for long enough to test this all properly and get things setup optimally, however you can see in this image I took first thing this morning the spicule ring and proms are much easier to see at the top half of the disk compared to the bottom half where we still have a ghost overlain.

Imagecak-full-disk-large-bw by Mark Townley, on Flickr

This obviously has the effect of robbing me of some exposure time, but is all workable. Longer term i'm looking at alternatives to the blockers i'm using to get more light throughput. All in all positive results and a move in the right direction me feels...


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Re: My PST CaK mod.

Post by Bob Yoesle »

Thank you very much for the link ( http://www.ray-optics.com/ ) and discussion Mark (W.) , a much better tutorial indeed!

Mark (T.) Very nice! - the double limb (again it is not a spicule ring -- it is the CaK chromopshere K2-K3 emission with photosphereic light leakage undernath as it were, just as in H alpha) is clearly visible all around the periphery of the disk, and good prominence detail. Do you attribute the improvement to the DS or use of the polarizer, or both? Have you tried the polarizer with a single stack to compare the results?

I'm getting the same type of "reflection" results, although in my case it must be coming from the use of the no. 2 filter (single stacked). On the other hand, I sometimes wonder if it might be due to some other effect -- perhaps camera-related -- as it always seems to be a "pulling" of light up & down the frame, as your image demonstrates, but usually more prominent is one direction verses the other. Is it possible there is some kind of excess UV leakage the camera is sensitive to that we are picking up and produces the "reflection" effect? Seems a little too consistent &/or coincidental in the location/orientation -- have you noticed this? I find it quite noticeable during the capture process.

Just food for thought (contrast adjusted to highlight effect):
CaK full disk enhanced.jpg


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Re: My PST CaK mod.

Post by swisswalter »

Hi Mark


I was not aware that you are throwing LUNT CaK stacks on to the sun , you better bring them to switzerland ;)

mark_caK-squarefilter14491166393_33c549c692_c_marked.jpg
mark_caK-squarefilter14491166393_33c549c692_c_marked.jpg (347.11 KiB) Viewed 7279 times


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Re: My PST CaK mod.

Post by Valery »

2 Mark T.

Before I buy a second CaK PST (for using it or DS), can you post some pairs of high resolution (as much as you do have) photos of the sun with SS vs DS photos
surace and prominences.
So, I will know exactly what I can expect from adding second main CaK filter (#1) to my CaK telescope train.

Thanks in advance.


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Re: My PST CaK mod.

Post by marktownley »

Hi All,

Sorry, slow to come back to the thread here...

Bob, must remember to call it the double limb - me bad! At the moment I haven't really had time (or the clear skies) to explore all the permutations that are possible with the elements in the filter. Certainly the double limb and the proms are much better seen when the filter unit is run double stacked and at f10. Much more contrast than single stack. The best thing to do Valery to look for comparisons is to have a look through the archives on my website. The whole 'CaK experiment' is documented on there often with more detail than I reflect with on here. The (linear) polariser does a decent job of removing some, but not all, of the reflections that make up the background glow in the sky. This background glow has the effect of losing contrast of proms and the double limb, you can see this effect well in the bottom of the image above compared to the top where the reflection isn't present.

In terms of the reflections i'm not sure why I get the outcome I do. I know If I hold the filter stack up to my eye and look to the sun I can see numerous ghost images. I guess this is attributed to the number of optical surfaces in the filter stack - 2x #1 CaK filters, a baader K-line (2 filters in this) and an EO 387/11nm filter.

When doublestacking the CaK filters the biggest issue you have is out of band blocking; In a single stack with 6% transmission (very nearly OD1) of filter #1 you can get away with just using a baader k-line, this combination works well. However doublestack 2 6% transmission filters and the transmission drops right down to 0.36% - about 1.5OD less, now, the transmission peak you're getting at 393nm is less than some of the out of band frequencies. So, to combat this you also then need to double stack the blockers... Problem then with all this is that the light throughput of the system drops, and with the increase of optical elements then also does the number of ghosts / reflections.

My current 'mission' with all this is to try and use different blockers than I have been using to let more light through and hopefully reduce the number of reflections; i'll let you all know how I get on...

Mark


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Re: My PST CaK mod.

Post by Valery »

My single stack system is quite simple - 394nm Edmund Optics + #1 CaK PST - excellent contrast and a lot of light.

So, to DS the #1 CaK PST I just need to DS the 394nm EO filter as well. But I think that even OD 2 blocker will be enough to save
the same level of contrast.


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Re: My PST CaK mod.

Post by marktownley »

Valery wrote:My single stack system is quite simple - 394nm Edmund Optics + #1 CaK PST - excellent contrast and a lot of light.

So, to DS the #1 CaK PST I just need to DS the 394nm EO filter as well. But I think that even OD 2 blocker will be enough to save
the same level of contrast.
Hi Valery,

Yes, that single stack system works perfectly. The important thing to realise here is when you double stack you are letting )approximately) OD1.5 less light through at 393.37nm, however the number one filter is pretty transparent with higher transmission across the rest of the spectrum, so you are not getting the same level of OD blocking here, and as such you need to compensate with more additional out of band blocking. Believe me, i've tried all this and speak from experience. My CaK filter works perfectly like your's in SS with the Baader K-line; I used it in this configuration for a couple of years, but, if you add in another #1 filter to double stack it doesn't work and the view is very washed out and lacking in contrast. The overall signal to noise ratio is worse which is why you need to add additional out of band blocking to get the contrast back. This is what is happening with Walter with his 'KLUNT' filter where he uses a Baader K-line with his Lunt CaK to get better contrast.

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Re: My PST CaK mod.

Post by Valery »

marktownley wrote:
Valery wrote:My single stack system is quite simple - 394nm Edmund Optics + #1 CaK PST - excellent contrast and a lot of light.

So, to DS the #1 CaK PST I just need to DS the 394nm EO filter as well. But I think that even OD 2 blocker will be enough to save
the same level of contrast.
Hi Valery,

Yes, that single stack system works perfectly. The important thing to realise here is when you double stack you are letting )approximately) OD1.5 less light through at 393.37nm, however the number one filter is pretty transparent with higher transmission across the rest of the spectrum, so you are not getting the same level of OD blocking here, and as such you need to compensate with more additional out of band blocking. Believe me, i've tried all this and speak from experience. My CaK filter works perfectly like your's in SS with the Baader K-line; I used it in this configuration for a couple of years, but, if you add in another #1 filter to double stack it doesn't work and the view is very washed out and lacking in contrast. The overall signal to noise ratio is worse which is why you need to add additional out of band blocking to get the contrast back. This is what is happening with Walter with his 'KLUNT' filter where he uses a Baader K-line with his Lunt CaK to get better contrast.

Mark
Mark,

My idea was that for bringing the contrast back with #1 DS, one need additional blocker and this blocker can be OD = 2 or so. Such a filter will cost less and will have higher transmission at the 393nm wave length.
Am I correct?

BTW. Mark, I sent you the e-mail. Please, read.


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Re: My PST CaK mod.

Post by Bob Yoesle »

I've obtained a second No. 1 CaK PST filter for some comparison trials.

Here's my optics chain: Orion (Skywatcher, etc.) ED100 F/9 refractor,

Baader Blue CDD filter (tilted) acting as a sub aperture ERF ~ 25 cm ahead of the CCD:
IMGP3219 crp.jpg
IMGP3219 crp.jpg (203.46 KiB) Viewed 7219 times
Baader CaK filter placed inside the PST filter housing acting as a bocking filter:
IMGP3222 SM.jpg
IMGP3222 SM.jpg (185.65 KiB) Viewed 7219 times
Then comes the original (still good!) No. 2 filter:
IMGP3225 SM.jpg
IMGP3225 SM.jpg (216.1 KiB) Viewed 7219 times
Then comes the original No. 1 filter in the PST housing (right), and the second No. 1, which is simply attached with silicone to the threaded ring (left):
IMGP3223 SM.jpg
IMGP3223 SM.jpg (299.63 KiB) Viewed 7219 times
This second No. 1 is screwed in behind the first, then placed in the existing DIY module, about 5 cm form the CCD (shown higher up in the adapter here for clarity):
Image2.jpg
Here are the identically processed images taken with my PGR Chameleon, generally poor conditions with nw winds @ 10-15 kph, temps in the mid to high 30's C:

Single stack @ 0.134 ms:
R_173142 single adj jpg.jpg
Double stack @ 0.438 ms:
R_173548 double adj jpeg.jpg
Single stack @ 0.134 ms:
R_174442 single adj jpg.jpg
Double stack @ 0.438 ms:
R_173827 double adj jpg.jpg
Here's a full-disk DS mosiac taken under even worse seeing conditions. Some "scattering" remains evident; I will be exploring this more when better conditions prevail:
full disk adj SM.jpg
At this point I think it is a worthwhile addition, though nowhere near the improvement seen with DSing H alpha filters. Perhaps the waveplate/polarizer solution is in order for taming the scattering/reflection. A small enough set of filters would seem to be able to fit between the two No. 1 filters, and the use of "optical grease" per Mark Wagner might assist as well...

Best wishes,

Bob
Last edited by Bob Yoesle on Mon Jul 07, 2014 6:33 am, edited 1 time in total.


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Re: My PST CaK mod.

Post by swisswalter »

Hi Bob

very fine results, congratulations


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Re: My PST CaK mod.

Post by Valery »

Thanks a lot, Bob, for your excellent comparision between DS and SS. It seems, that I will need a second #1 CaK filter ASAP.


Valery.


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Re: My PST CaK mod.

Post by Bob Yoesle »

Thanks Walter and Valery,

I had some good seeing this morning and managed a good comparison image between continuum and CaK DS on AR 2109:
AR 2109 WL v  CaK.jpg
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Re: My PST CaK mod.

Post by swisswalter »

Hi Bob

a very fine comparison


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Re: My PST CaK mod.

Post by Bob Yoesle »

Thank you Walter!

So looking at the reflection suppression issue, per Mark (W.) we seem to need a linear polarizer coupled to a 1/4 wave plate, and an optical coupling compound would be nice too.

Checking the usual suspects for such gear, the prices become a bit on the high side -- $500 to $1000 + USD minimum for the pair:

http://www.thorlabs.com/navigation.cfm?guide_id=8

http://search.newport.com/i/1/q1/produc ... pter/nav/1

Then I found a nice little article that opens the door to a possible and more economical solution:

http://www.bobatkins.com/photography/te ... izers.html

Thus photographic circular polarizers might be a possible solution, if of high enough quality -- they incorporate a linear polarizer and a 1/4 waveplate together in a single filter. I checked a bit on these and a couple of candidates in the appropriate sizes might be a B&W:

http://www.bhphotovideo.com/c/product/6 ... cular.html

or a Zeiss:

http://www.bhphotovideo.com/c/product/9 ... ilter.html

So I would like some advice or constructive critique - why would not these be worth a try? While likely not optimized for UV, not much else in the professional laser optics variety are either. It seems that a little "optical grease" of the "ecomomical option" -- http://www.logwell.com/tech/servtips/op ... rease.html
could be employed to make a CaK filter "sandwich" which might further reduce reflections... And there's this stuff as well, which is fairly cheap in a small quantity: http://www.advgauging.com/Merchant5/mer ... lectronics

Thoughts???


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Re: My PST CaK mod.

Post by swisswalter »

Hi Bob

thank you very much for your information. Very interesting I dive into it and visit the links


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Re: My PST CaK mod.

Post by Valery »

Bob Yoesle wrote:Thank you Walter!

So looking at the reflection suppression issue, per Mark (W.) we seem to need a linear polarizer coupled to a 1/4 wave plate, and an optical coupling compound would be nice too.

Checking the usual suspects for such gear, the prices become a bit on the high side -- $500 to $1000 + USD minimum for the pair:

http://www.thorlabs.com/navigation.cfm?guide_id=8

http://search.newport.com/i/1/q1/produc ... pter/nav/1

Then I found a nice little article that opens the door to a possible and more economical solution:

http://www.bobatkins.com/photography/te ... izers.html

Thus photographic circular polarizers might be a possible solution, if of high enough quality -- they incorporate a linear polarizer and a 1/4 waveplate together in a single filter. I checked a bit on these and a couple of candidates in the appropriate sizes might be a B&W:

http://www.bhphotovideo.com/c/product/6 ... cular.html

or a Zeiss:

http://www.bhphotovideo.com/c/product/9 ... ilter.html

So I would like some advice or constructive critique - why would not these be worth a try? While likely not optimized for UV, not much else in the professional laser optics variety are either. It seems that a little "optical grease" of the "ecomomical option" -- http://www.logwell.com/tech/servtips/op ... rease.html
could be employed to make a CaK filter "sandwich" which might further reduce reflections... And there's this stuff as well, which is fairly cheap in a small quantity: http://www.advgauging.com/Merchant5/mer ... lectronics

Thoughts???
Thanks, Bob, for your efforts in this project. Thoughts? My thought is that this is not so much necessary. If to use such a rig, then no necessity in fight against relections. B-CCD Baader ERF (also blocks geen and longer wave lengths) > K-line Baader > #1 CaK PST (both in the body of the #1 PST) > #1 PST (second one).

The pair K-line + #1 CaK PST has tilt in the cell and must be about 190mm from the camera - so the relection will not overlap the main sun disk image. This is important. Then a second #1 CaK PST should be in 50mm from the camera. All is about F/10 telescope.

When I do use very similar rig, I see no ghost image overlapped the Sun image. #2 PST > #1 PST > 140mm gap > Edmund Optics 11nm blocker.


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Re: My PST CaK mod.

Post by sullij1 »

Bob, Thanks for the detailed information. It will help with another project I am toying with.

Valery, thanks for the input on spacing etc.


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Re: My PST CaK mod.

Post by Bob Yoesle »

Hi Joe, glad to help.

I've found another variation of the B+W circular polarizers -- the Kaesemann variant is stated to:
The “high-end” polarizing foils of the Käsemann-type filters are neutral in color, they have a higher efficiency than conventional polarizing foils and they are cemented between high-grade plano-parallel optical glass. The resulting sandwich is then precision-polished again to achieve highly accurate plano-parallel surfaces. Subsequently they are edge-sealed to protect the foil against humidity... They are well suited for applications that require the highest possible imaging quality, especially with high-speed telephoto lenses and apochromatic lenses.
http://www.bhphotovideo.com/c/product/1 ... izing.html

Bob
Last edited by Bob Yoesle on Thu Jul 10, 2014 4:45 pm, edited 1 time in total.


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Re: My PST CaK mod.

Post by swisswalter »

Hi Bob

thank you very much, more interesting stuff


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Re: My PST CaK mod.

Post by Bob Yoesle »

You're welcome Walter. I'm thinking some of my CaK scatter may be coming from my No.2 filter, and will try some images without it ASAP.

Also of note: Lunt appears to be implementing a similar method of using a polarizer between internal etalons to improve the performance of it's double stacking H alpha modules. Since these filters are available in sizes from 37 mm to over 100 mm, they might be worth checking out for the suppression on H alpha reflections between etalons as well.

http://www.bhphotovideo.com/c/product/1 ... izing.html

Bob


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Re: My PST CaK mod.

Post by swisswalter »

Hi Bob

an interesting thought


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Re: My PST CaK mod.

Post by Valery »

Bob Yoesle wrote:I'm thinking some of my CaK scatter may be coming from my No.2 filter, and will try some images without it ASAP.
My findings as follow: the least scatter rig: Edmund Optics 11nm blocker > #1 PST CaK > 140mm gap> #2 PST CaK> 50mm gap > camera


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Re: My PST CaK mod.

Post by Bob Yoesle »

Hi Valery, thanks for that ;-)

I ended up removing the No. 2 filter from my filter system, as it appears redundant and has a slight amount of cloudiness. This seems to have improved my imaging results.

Here's my "New" CaK module:
CaK DS Module New.jpg
It now consists of the Baader Blue CCD filter (tilted) acting as a sub-aperture ERF > 205 mm gap > Baader CaK filter > 5 mm gap > PST No. 1 filter > 60 mm gap > PST No. 1 filter (tiltable) > 60 mm gap > CCD chip.

I'm utilizing a prototype Skybender tilt module: http://www.cloudynights.com/ubbthreads/ ... in/6403755 . It has a 1.25 inch nosepiece which is threaded for standard 1.25 inch filters; this is what the Badder CaK and piggybacked first No. 1 filter are attached to. Then it has an internal adjustable tilt filter holder to which I've attached the second No. 1 filter. I adjusted the tilt to produce the best contrast with the second No. 1 fiter, I don't think it's too far off from being normal to the optical axis. Here you can see the Baader CaK filter, and just below it is piggybacked a rotating 1.25 inch polarizer filter holder with the first No.1 filter. The second No.1 filter is similarly mounted in a standard 1.25 inch filter holder, attached to the internal tilt plate:
Skybender SM.jpg
The Skybender system and filter holders shown above give me the ability to rotate the first and second No.1 filters with respect to each other, and tilt the soon to be purchased circular polarizer.

Here are my results from earlier today - Orion ED100 f/9 at prime focus in fair seeing:

Single stack No. 1
R_180141 jpeg adj.jpg
Double stacked No. 1's:
R_180330 jpeg adj.jpg

There is still some residual light scatter -- I'll be testing a circular polarizer in the tilt mechanism as shown in the ISOON telescope -- and placing the second No. 1 filter a bit closer to the CCD sensor... we'll see if this makes a significant improvement, or if tilting the second No. 1 filter alone is sufficient.
isoon_optics crp.jpg
isoon_optics crp.jpg (140.5 KiB) Viewed 7123 times
Again, pretty conclusive that just as with H alpha, we have less photosphere and more chromopshere detail with the DS CaK filter system.

Best wishes,


Bob


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