My PST CaK mod.

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My PST CaK mod.

Post by Valery »

Hi all, the modders!


I recently bought a very little used PST CaK. Looks like new, unused. But I don't know it's real age.

OK, I like to modify it as soon as possible.

Is such an Omega filter will be sufficient to work as a blocker as a mate element to the main CaK filter of the PST?

Do I need more filters (except ERF in a front of the mod module) ?

Thanks in advance to all, who will try to help with suggestions.


Valery.
Last edited by Valery on Wed Jun 04, 2014 8:01 pm, edited 3 times in total.


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Re: My PST CaK mod. Help!

Post by swisswalter »

Hi Valery

you need an suitable ERF up front (DERF will not work) or a hot mirror down the train. A blocking filter is not needed but something like a K-line filter improves the imaging


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Re: My PST CaK mod. Help!

Post by marktownley »

Good man Valery! :cool:

Don't use the Omega stuff, in my experience there is so much variation in quality. In terms of blockers a Baader K-Line and / or a Baader U (venus filter) are what I consider to be the minimum. The quality is so much higher with the baader stuff.

What did you have in mind for an ERF?


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Re: My PST CaK mod. Help!

Post by Valery »

marktownley wrote:Good man Valery! :cool:

Don't use the Omega stuff, in my experience there is so much variation in quality. In terms of blockers a Baader K-Line and / or a Baader U (venus filter) are what I consider to be the minimum. The quality is so much higher with the baader stuff.

What did you have in mind for an ERF?
We do have here some filters made for 393nm with 8nm with about 67% to 80% transmission. D=18mm. May be I will use this filter. Baader is very expensive if include all the shipping and import duty cost + dealer cost.

As for ERF. I hope to make flat filter from the locally available glasses which are close to Schott BG12 and BG25 glasses.

The first our glass suitable for ERF for CaK has 77% at 393nm and 0% at 320nm and 500nm, the second glass has 74% at 393nm and 0% at 330nm and 490nm and the third glass suitable for Cak has 82% at 393nm, 0% at 320nm and 490nm.

The first glass has the smallest red leak with Tmax 3,5% at 1080nm and 1% at 900nm and 1300nm. It seems to be the best ERF among all our glasses.

I will ask our optical plant about at the stock availability.


Valery


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Re: My PST CaK mod. Help!

Post by marktownley »

Out of band blocking is one of the keys to getting a higher contrast image.

I have tried BG25 and found it to be not very flat optically. Don't forget these shorter wavelengths are much more sensitive to wavefront error than the longer wavelengths.

Best ERF I would recommend is a solar wedge without any ND filters in it. With a single stack cak filter you will have more than adequate throughput of light even with the 5% transmission of the wedge.


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Re: My PST CaK mod. Help!

Post by Valery »

marktownley wrote:Out of band blocking is one of the keys to getting a higher contrast image.

I have tried BG25 and found it to be not very flat optically. Don't forget these shorter wavelengths are much more sensitive to wavefront error than the longer wavelengths.

Best ERF I would recommend is a solar wedge without any ND filters in it. With a single stack cak filter you will have more than adequate throughput of light even with the 5% transmission of the wedge.
I didn't realize where I have the light loss in my PST CaK that my exposures (with 1,5x Barlow and 44% camera QE at the 393nm) is 1/20 sec duration! If this the problem with the CaK PST main filter then I need to save every % of the light and better to use a UV or dark blue ERF than a Hershel prism where I will loss 96% of energy across the spectrum.


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Re: My PST CaK mod. Help!

Post by marktownley »

Valery wrote:better to use a UV or dark blue ERF
If you find one of decent aperture and optical quality then let us know, we've been looking for some considerable time to no avail. The biggest and best so far is the Beloptik triband - currently only 85mm max.


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Re: My PST CaK mod. Help!

Post by Valery »

Hi Mark,

Do you think this Edmund filter (hard coated) will be better choice than a Baader K-line filter?
The reason I think so that it has 85% transmission at the CWL 394nm and it is hard coated - for a long life.
It is $195 in 25mm size ( $120 in 12.5mm ) while the K-line Baader is $330 for the same 32mm diameter.

For my present camera (PGR Flea 3) a 12.5mm size is enough - I can place the filter near the camera window - so there will
be no vignetting. However I need to look in a future and may be new CMOSis cameras with larger chips
and low noise will play a first role soon in a future.


Thanks,

Valery.


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Re: My PST CaK mod. Help!

Post by swisswalter »

Hi Valery

with a WO 110 f/6 i fried sucessfully a K-line and a Beloptik filter. You have to have something cutting the load up the train or better up front


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Re: My PST CaK mod. Help!

Post by marktownley »

Valery wrote:Hi Mark,

Do you think this Edmund filter (hard coated) will be better choice than a Baader K-line filter?
The reason I think so that it has 85% transmission at the CWL 394nm and it is hard coated - for a long life.
It is $195 in 25mm size ( $120 in 12.5mm ) while the K-line Baader is $330 for the same 32mm diameter.

For my present camera (PGR Flea 3) a 12.5mm size is enough - I can place the filter near the camera window - so there will
be no vignetting. However I need to look in a future and may be new CMOSis cameras with larger chips
and low noise will play a first role soon in a future.


Thanks,

Valery.
Hi Valery.

Yes, I see no reason why it won't work. I use the EO 387/11nm filter in my double stack with the K-line, they're the same type of hard coated filter. With the additional 387nm in the setup contrast is higher - I think this is down to the out of band blocking improving the signal to noise.

Walter is right about cutting the thermal load - I have seen his ill fated K-line :D Seriously, get the yellowy CaK filter from the PST, use with a K-line / EO filter and a wedge without any ND filters, it will work and will be bright enough - trust me! Even if the maths seems to suggest it wont it will work. Here is a link written by Jen at daystar saying how a solar wedge won't work with CaK - it might not with a Daystar filter, but it will with what you are doing http://ukastroimaging.co.uk/forums/inde ... #msg337552

The only thing I would say with the smaller filter you are talking about is it won't give you much flexibility to move it up and down the optical train if reflections turn out to be a problem.

Keep modding!

Mark


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Re: My PST CaK mod. Help!

Post by Valery »

swisswalter wrote:Hi Valery

with a WO 110 f/6 i fried sucessfully a K-line and a Beloptik filter. You have to have something cutting the load up the train or better up front
Hi Walter!

Thanks for your info. I will use one of three solutions here:

1. Full size ERF (color glass made by local optical plant)
2. Full size D-ERF (for two bands 656nm and 393nm, may be a third wave length for white light imaging).
3. sub-aperture 50mm Baader CCD RG filter (as suggested by our friend Bob Yoesle).

But I will not use it without any of these filters. I will re-do the PST CaK (remove the black box with pentaprism) -
use the same objective and small helical focuser - for full disk imaging.


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Re: My PST CaK mod. Help!

Post by Valery »

marktownley wrote: Seriously, get the yellowy CaK filter from the PST, use with a K-line / EO filter and a wedge without any ND filters, it will work and will be bright enough - trust me! Even if the maths seems to suggest it wont it will work. Here is a link written by Jen at daystar saying how a solar wedge won't work with CaK - it might not with a Daystar filter, but it will with what you are doing http://ukastroimaging.co.uk/forums/inde ... #msg337552

The only thing I would say with the smaller filter you are talking about is it won't give you much flexibility to move it up and down the optical train if reflections turn out to be a problem.

Keep modding!

Mark
Hi Mark,

Thanks for your suggestions. However I will not use it with Hershel prism - remember what I wrote earlier that through a native PST CaK I imaged at F/12-15, no any Hershel prism and my exposures are 1/30 sec and with good portion of a gain! So, I need to fight for each % of light!

Possibly my main CaK PST filter is rusted and blocks too much light. I still hope that this is my bad barlow lens with
inappropriate coating which filters the light. If so, then I will buy a Hershel prism and use the 8" F/10 SCT or a 6" F/5 refractor + 2x - 3x Barlow.

We will see later this month.


Mark, still the question.

Do you suggests that I need to buy a EO 387nm hard coated filter instead of EO 394nm hard coated?
Or do I need to use both?


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Re: My PST CaK mod. Help!

Post by marktownley »

Hi Valery.

I don't know how much you have disassembled your CaK PST but there are 4 separate filters in it. I've indicated their position in the image below:
P1080261.jpg
P1080261.jpg (267.76 KiB) Viewed 5983 times
The only filter you need from the CaK PST is filter 1, here is a pic below, it is the 'yellow filter' I was referring to above.
1.jpg
1.jpg (235.29 KiB) Viewed 5983 times
The rest of the filters in the CaK PST are junk, they rust and rob the light! Here, I will show you...

Here is filter number 2, you can see the rust spots around the edge, it's not too bad in this one, but my other CaK PST is rusted to the centre of the filter...
2.jpg
2.jpg (266.72 KiB) Viewed 5983 times
Next up is filter number 3 in the base of the eyepiece holder. This one rusts also!
3.jpg
3.jpg (312.76 KiB) Viewed 5983 times
Finally, the filter you can see in the eyepiece holder is a UV cut filter.
4.jpg
4.jpg (156.78 KiB) Viewed 5983 times
Now, the ONLY filter you need here is filter 1. The rest are robbing your light, do not use them! Using filter 1 with a Baader K line and wedge with no ND filters WILL give you an exposure 10-30x faster than what you are getting with the CaK PST at f12-15, you have to just trust me and try this!

Regards the 387/11nm filter it won't work on it's own with the Yellow caK PST filter, the yellow caK PST filter has a sideband leak in the 387nm filters pass band, and so you get a washed out image, but with the K-line it shows an improvement over just using the K-line on itself.

Hope this helps!

Mark


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Re: My PST CaK mod. Help!

Post by Valery »

Mark,

Many many thanks for your so detailed and complete clarification. I will disassemble my PST CaK again and see if the yellowing main filter is OK and not rusted. If OK, I will immediately order the EO 494nm filter and may be also the EO 387nm. Then it will be easy to make the final step.

Valery.


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Re: My PST CaK mod. Help!

Post by marktownley »

Filter number 1, the yellow filter, will not rust, it is not a laminate filter with soft coating.


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Re: My PST CaK mod. Help!

Post by Valery »

marktownley wrote:Filter number 1, the yellow filter, will not rust, it is not a laminate filter with soft coating.
Wooo hooo! Nice! This mean I can order the other components early next week!
Thanks again, Mark!

You definitely need to create a guide for all PST CaK mod-ders - this will save a lot of time and eyes.
Last edited by Valery on Sun May 11, 2014 2:11 pm, edited 1 time in total.


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Re: My PST CaK mod. Help!

Post by marktownley »

I look forward to seeing your results Valery, in particular how you get on with the EO393, i've thought about getting one of these a few times now myself...


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Re: My PST CaK mod. Help!

Post by swisswalter »

Valery wrote:
swisswalter wrote:Hi Valery

with a WO 110 f/6 i fried sucessfully a K-line and a Beloptik filter. You have to have something cutting the load up the train or better up front
Hi Walter!

Thanks for your info. I will use one of three solutions here:

1. Full size ERF (color glass made by local optical plant)
2. Full size D-ERF (for two bands 656nm and 393nm, may be a third wave length for white light imaging).
3. sub-aperture 50mm Baader CCD RG filter (as suggested by our friend Bob Yoesle).

But I will not use it without any of these filters. I will re-do the PST CaK (remove the black box with pentaprism) -
use the same objective and small helical focuser - for full disk imaging.

Hi Valery

I'm also interested in Version 1 ;)

if you mean by D-ERF the baader type, that will not work, Zero Transmission at 393 and 396 nm


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Re: My PST CaK mod. Help!

Post by Valery »

swisswalter wrote:
I'm also interested in Version 1 ;)

if you mean by D-ERF the baader type, that will not work, Zero Transmission at 393 and 396 nm
1. I guess too, that absolutely most of solar imagers will be interested in full size ERF filter as this is the most safe solution and the life time as well.

2. D-ERF - I do mean Dielectric ERF, not necessary mean that Baader's D-ERF for Ha imaging/observing only.
I hope that a filter, like Beloptic's three-band, can be created as full size aperture.

We will see what will works best for us. May be the cheapest and most reliable way will be still two ERFs for 393 and 656nm.


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Re: My PST CaK mod. Help!

Post by Valery »

Mark,

Can you, please, tell the sequence and approximate spaces in your CaK double stack rig?
And how can you get rid of reflections/ghosts in this rig?

I asking because if all is OK with my main "yellowing" Cak PST element, I would by one more CaK PST to take one more such element for DS. If to have a CaK telescope, better to have the best of the best if I can afford (and I can).

Thanks,

Valery.


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Re: My PST CaK mod. Help!

Post by marktownley »

Hi Valery, all details including spacings can be seen in the image I posted in this thread.

http://solarchat.natca.net/viewtopic.php?f=9&t=11342

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Re: My PST CaK mod. Help!

Post by Valery »

marktownley wrote:Hi Valery, all details including spacings can be seen in the image I posted in this thread.

http://solarchat.natca.net/viewtopic.php?f=9&t=11342

Mark
Thanks, Mark.

Have you get rid of the ghosts/reflections between the two CaK PST ?




Valery.


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Re: My PST CaK mod. Help!

Post by marktownley »

Yes, the more distance between them the better.


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Re: My PST CaK mod. Help!

Post by Valery »

marktownley wrote:Yes, the more distance between them the better.

There is a limiting factor for the distance - a small diameter of these filters, a required unvignetted field (sun disk) and an F/ratio of the system. As slower the system, as larger the distance can be. There is a compromise. It is useful to make the module which can be put in a different telescopes.
Last edited by Valery on Mon May 12, 2014 3:06 am, edited 1 time in total.


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Re: My PST CaK mod. Help!

Post by marktownley »

I think in my module they're about 150mm apart.


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Re: My PST CaK mod. Help!

Post by Valery »

marktownley wrote:I think in my module they're about 150mm apart.
Hi Mark!

Hope that below questions are the last ones and after the answers I will have in my head a completely clear picture of what to do with the CaK PST mod.

1. How have you get rid of the ghosts? Have you inclined both components (of this pair of CaKPST) in opposite direction or you just rotate (clocking) related to each other?

2. You рфму noted several times that the contrast in the DS is higher than in the SS. Is the contrast increasing in the DS can be then reached in the SS during post processing of the images? Or the contrast in the DS is of a principal character - you see new delicate details/structures/prominences that can't be extracted from the images (by post processing) in the SS?

3. Same question about principality of the contrast increasing regarding using additional EO 387nm filter.

Thanks!


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Re: My PST CaK mod. Help!

Post by marktownley »

Hi valery.

I found that just getting as much distance between the 2 filters was the way forward, the ghost / reflection just became more diffuse and dimmer when I did this. If I tilted one of the filter elements (when they were located close together) it moved the ghost reflection, but the image was dimmer and you could see losing detail as its bandpass shifted blueward off 393.37nm.

With regards to contrast; basically what you are seeing is the disk itself becomes darker, the plage (relative to the disk) is much brighter, super granulation cells are much easier to see, the plage itself can be seen to have its own dynamic range of levels - ie it is not just bright white, and prominences are fairly easy to see. Filaments and filaproms can be started to be hinted at, as are a range of other loop structures on the surface. The vast majority of this cannot be extracted in post processing with a single stack.

Regards the EO 387, this darkens the disk off, while preserving the highlights, just improving disk contrast.

No probs with the questions, just ask away!

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Re: My PST CaK mod. Help!

Post by Valery »

marktownley wrote:Hi valery.

I found that just getting as much distance between the 2 filters was the way forward, the ghost / reflection just became more diffuse and dimmer when I did this. If I tilted one of the filter elements (when they were located close together) it moved the ghost reflection, but the image was dimmer and you could see losing detail as its bandpass shifted blueward off 393.37nm.

With regards to contrast; basically what you are seeing is the disk itself becomes darker, the plage (relative to the disk) is much brighter, super granulation cells are much easier to see, the plage itself can be seen to have its own dynamic range of levels - ie it is not just bright white, and prominences are fairly easy to see. Filaments and filaproms can be started to be hinted at, as are a range of other loop structures on the surface. The vast majority of this cannot be extracted in post processing with a single stack.

Regards the EO 387, this darkens the disk off, while preserving the highlights, just improving disk contrast.

No probs with the questions, just ask away!

mark :)
Hi Mark!

Thanks again!

Can you show us here the photos where you point out (by arrows) all these new features of the sun surface not visisble with SS.
very interesting, ideed.

Today I will visit my island observatory ( 50m above the ground) with very wide river delta in front (lower turbulence) and will
take the PST CaK home and will see it's "guts". If the "yellowing" CaKPST filter is OK, then I will order both EO filters 394 and 387nm
and will place start to seek a second CaK PST.

Valery.
Last edited by Valery on Mon Jun 09, 2014 5:51 am, edited 1 time in total.


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Re: My PST CaK mod. Help!

Post by Valery »

CaK Colonel Mark Townley! Sir, allow me to report the results of investigation of the facility PST CaK!
The secret part of the object, namely, the filter CaK PSTmain, looks unharmed.
The campaign "PST CaK Modification-2" looks safe and easy. Losses are not expected. :^)

CaK Сaptain Valery.


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Re: My PST CaK mod. Help!

Post by thesmiths »

Mark: what do you estimate the bandwidth is of the double stack PST-CaK mod? Do you also know at wavelength the bandwidth is centred? Perhaps these numbers were mentioned elsewhere but as posts get revised, it's difficult to know what data is current.

I ask because for my next SHG Ca-K experiment, I would like to start with a "known good bandwidth" and then see how well the images can be improved. I sense with Ca-K, when the bandwidth is too small (below 0.5 angstrom), the images start to look a bit bland. The problem/advantage of the SHG is the addressable parameter space is gigantic.


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Re: My PST CaK mod. Help!

Post by marktownley »

Hi folks.

Valery, yes, I will get some pics up with comparisons etc. Good to know the main filter has been removed successfully, now the fun begins for you ;)

The bandwidth of the DS CaK is ~1.57a based upon the original filters being 2.2a each. The 1.57a compares identically with images from the Paris Meudon which is a (known) bandwidth of ~1.5a. The bandpass is centred on 393.37nm - I have been able to blue shift this by tilting the filters, and also redshift it by heating them - it is very noticeable in my eyes when the filters central bandpass goes off 393.37 as contrast and detail falls away rapidly...


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Re: My PST CaK mod. Help!

Post by Valery »

thesmiths wrote:Mark: what do you estimate the bandwidth is of the double stack PST-CaK mod? Do you also know at wavelength the bandwidth is centred? Perhaps these numbers were mentioned elsewhere but as posts get revised, it's difficult to know what data is current.

I ask because for my next SHG Ca-K experiment, I would like to start with a "known good bandwidth" and then see how well the images can be improved. I sense with Ca-K, when the bandwidth is too small (below 0.5 angstrom), the images start to look a bit bland. The problem/advantage of the SHG is the addressable parameter space is gigantic.
Hi,

Can you, please, tell us what does it states for - the SHG ?

And what did you mean here: "The problem/advantage of the SHG is the addressable parameter space is gigantic" ?
Last edited by Valery on Tue May 13, 2014 10:24 am, edited 1 time in total.


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Re: My PST CaK mod. Help!

Post by Valery »

marktownley wrote:Hi folks.

Valery, yes, I will get some pics up with comparisons etc. Good to know the main filter has been removed successfully, now the fun begins for you ;)

The bandwidth of the DS CaK is ~1.57a based upon the original filters being 2.2a each. The 1.57a compares identically with images from the Paris Meudon which is a (known) bandwidth of ~1.5a. The bandpass is centred on 393.37nm - I have been able to blue shift this by tilting the filters, and also redshift it by heating them - it is very noticeable in my eyes when the filters central bandpass goes off 393.37 as contrast and detail falls away rapidly...

Mark, with all respect, I didn't see the tilt mechanism in your CaK DS rig. How have you tilted the filters? How have you checked the band pass shift?

Then, how have you heated the filters to red shift them?

Can you describe all these procedures in details. It is always nice to read how enthusiasts performs their experiments, especially if they succeeded.

It will be useful to me to know the details as I would like to design and mill the accessory which will keep the filters correctly orientated all the time.

And what to do if the filters will blue shift in a cold weather?

And the last. You know, that aperture, say, F/10 is not a parallel beam and CWL will shifts for edges of aperture vs the center. In other words, we do need a telecentric system.


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Re: My PST CaK mod. Help!

Post by Valery »

BTW Mark, I didn't find the EO 387nm filter at their website. Can you link me to that filter?

Thanks,

Valery.


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Re: My PST CaK mod. Help!

Post by thesmiths »

Valery: SHG = spectroheliograph. The parameter space is gigantic size because any bandwidth and centre wavelength can be chosen. That is in addition to the normal optical and atmospheric issues. And of course data acquisition is relatively slow and post-processing time relatively long. Ca-K is a good place to start with SHG since the bandwidth requirements are not particularly high. 1 angstrom is easy.


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Re: My PST CaK mod. Help!

Post by marktownley »

I finally found my other 'number 2' CaK filter, showing the rusting that has crept in from the edges...
P1080287.jpg
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Re: My PST CaK mod. Help!

Post by marktownley »

Valery wrote:Mark, with all respect, I didn't see the tilt mechanism in your CaK DS rig. How have you tilted the filters? How have you checked the band pass shift?

Then, how have you heated the filters to red shift them?

Can you describe all these procedures in details. It is always nice to read how enthusiasts performs their experiments, especially if they succeeded.

It will be useful to me to know the details as I would like to design and mill the accessory which will keep the filters correctly orientated all the time.

And what to do if the filters will blue shift in a cold weather?

And the last. You know, that aperture, say, F/10 is not a parallel beam and CWL will shifts for edges of aperture vs the center. In other words, we do need a telecentric system.
I tilted the filters in the cells that housed them, you would not see it externally. A long process - disassemble housing, tilt filter, reassemble housing, image, repeat and so on... The filter elements are best kept perpendicular to the optical axis, it is the spacings you need to experiment with.

I tried heating with dew heaters - demonstrates the effect but virtually impossible to control.

Not much we can do in extreme hot or cold weather though!

Yes, there is a small CWL shift from centre to edge of the field of view, you can see it in the form of a slight variance in brightness of the image. I am certain the PST cak filters are designed to operate at f10, you saw the series of full disks I took in april, and I have also tried running the CaK filters in a collimated beam (as with a Ha PST mod) - the image was poor and lacking in contrast with this. IMHO f10 is the only way to go with CaK PST filters.


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Re: My PST CaK mod. Help!

Post by Valery »

marktownley wrote:I finally found my other 'number 2' CaK filter, showing the rusting that has crept in from the edges...
P1080287.jpg
Hi Mark!

Is this a "yellowing" key filter or this is a #2 filter counting from the objective?


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Re: My PST CaK mod. Help!

Post by Valery »

marktownley wrote:
1. Not much we can do in extreme hot or cold weather though!

2. Yes, there is a small CWL shift from centre to edge of the field of view, you can see it in the form of a slight variance in brightness of the image. I am certain the PST cak filters are designed to operate at f10, you saw the series of full disks I took in april, and I have also tried running the CaK filters in a collimated beam (as with a Ha PST mod) - the image was poor and lacking in contrast with this. IMHO f10 is the only way to go with CaK PST filters.
1. Why not make a heated owen with thermo-probe in it and good thermal insulation? This is for winter condition.
My PST still work (in band) at 28C and more at the direct sun. So, only a cold weather now is hazardous for my CaK. I will see what can I do in a winter.


2. You can't say anything with confidence how well corrected for SA was your collimation + refocusing system. May be problem was there?

In a future I will try to design and make a sample of a collimator-refocuser with SA nullified at 393nm. May be all will be OK and the band wide can become even narrower? Why know? Our chances are 50/50. It is relatively easy for me to try, in near future.

Now I am waiting for the EO 394nm 11nm block filter arrival and then I will go ahead to make the CaK telescope. 77mm pre-filter (Hoya 80A) was purchased already too and is on the way to me.


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Re: My PST CaK mod. Help!

Post by marktownley »

Hi Valery - a thermo oven and probe, sounds like too much hassle to me... I think my filter setup holds its own...

The only thing I can say about SA in the different combinations i've used is that I can recognise when the SA is poor, and I can recognise when it it better, not saying it is perfect though. At the end of the day the setups i'm making are from off the shelf components and bits and pieces from my box of spares...


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Re: My PST CaK mod. Help!

Post by swisswalter »

Valery wrote:
In a future I will try to design and make a sample of a collimator-refocuser with SA nullified at 393nm. May be all will be OK and the band wide can become even narrower? Why know? Our chances are 50/50. It is relatively easy for me to try, in near future.

.
Hi Valery

I'm very much interested in that SA corrector. Better today, then tomorrow ;)


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Re: My PST CaK mod. Help!

Post by Valery »

Mark,

May I ask you again (you forget to answer) - is this the "yellowing" key CaK filter on the last photo (rusted) or this is the next (#2) filter after the "yellowing" one
if count from the telescope objective?


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Re: My PST CaK mod. Help!

Post by Valery »

swisswalter wrote:[quote="Valery

In a future I will try to design and make a sample of a collimator-refocuser with SA nullified at 393nm. May be all will be OK and the band wide can become even narrower? Why know? Our chances are 50/50. It is relatively easy for me to try, in near future.

.
Hi Valery

I'm very much interested in that SA corrector. Better today, then tomorrow ;)[/quote]

Walter,

The SA corrector for 393nm can be designed for a specific telescope only because a SA at the 393nm is different in different telescopes.
The same with a collimation - refocusing optics with nullified SA at 393nm - it can be designed for a specific refractor only.

We need to choose the donor telescope. We can make a small series of such correctors for a specific telescope we will choose.
And we need at least 10 persons who will order such a device to justify the manufacturing cost of such a small series. Better 20 persons.

Regards,

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Re: My PST CaK mod. Help!

Post by swisswalter »

Hi Valery

thank you very much for your feed back. I understand and I see there is no easy solution for me. I have now about 15 scopes here and all of them wait to be tested and used with CaK mods ;)


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Re: My PST CaK mod. Help!

Post by Valery »

swisswalter wrote:Hi Valery

thank you very much for your feed back. I understand and I see there is no easy solution for me. I have now about 15 scopes here and all of them wait to be tested and used with CaK mods ;)
Hi Walter,

I think this is a wrong way for you NOW, when you knew me and I am nearby. :D

IMHO, the best way for many of us, CaK gangs, is to choose a right (compact, universal, inexpensive, powerful, refractor) telescope and design and make a small batch of CaK correctors for 1x or for 1,5x or for 2x. In this case such a scope can be used according it's original purpose and for detailed CaK imaging.

IMHO-2 Such a telescope is a Sky Watcher 150mm F/750mm refractor. It has HUGE spherical aberration at 393nm, but corrector will produce almost ideal correction up to Strehl 0.98. Also a correctors for 656nm is possible and a must.

IMHO-3 as joke, If you sell all these 15 telescopes there will be earned enough money for such a specialized universal telescope - TOA-150. Ih has excellent correction at 656nm and acceptable (acceptable) correction at 393nm.


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Re: My PST CaK mod. Help!

Post by swisswalter »

Valery wrote:
swisswalter wrote:Hi Valery

thank you very much for your feed back. I understand and I see there is no easy solution for me. I have now about 15 scopes here and all of them wait to be tested and used with CaK mods ;)
Hi Walter,

I think this is a wrong way for you NOW, when you knew me and I am nearby. :D

IMHO, the best way for many of us, CaK gangs, is to choose a right (compact, universal, inexpensive, powerful, refractor) telescope and design and make a small batch of CaK correctors for 1x or for 1,5x or for 2x. In this case such a scope can be used according it's original purpose and for detailed CaK imaging.

IMHO-2 Such a telescope is a Sky Watcher 150mm F/750mm refractor. It has HUGE spherical aberration at 393nm, but corrector will produce almost ideal correction up to Strehl 0.98. Also a correctors for 656nm is possible and a must.

IMHO-3 as joke, If you sell all these 15 telescopes there will be earned enough money for such a specialized universal telescope - TOA-150. Ih has excellent correction at 656nm and acceptable (acceptable) correction at 393nm.

Hi Valery

thank you for your "IMHO's" I have such a scope AP 155 f/7 ;)


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Re: My PST CaK mod. Help!

Post by marktownley »

Valery wrote:Mark,

May I ask you again (you forget to answer) - is this the "yellowing" key CaK filter on the last photo (rusted) or this is the next (#2) filter after the "yellowing" one
if count from the telescope objective?
Hi Valery,

The picture I added is the "number 2" filter (as in the photo of the CaK PST earlier in the thread. It is not the magic CaK filter that we need (filter number 1). The rusted filters can be thrown away.

Has your EO filter arrived yet? I am contemplating getting a EO 394nm filter and giving it a try instead of the Baader K-line - fewer optical surfaces etc...

Mark


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Re: My PST CaK mod. Help!

Post by Valery »

Thanks, Mark, for your clarification about the picture. I now feel much better than before when I think this was the magic "yellowing glass" (YG) TM.

My filter #2 looks absolutely the same as your one.

My EO still on the way with other goods ordered by my agent for his business. Slow boat is cheaper for him (and for me) and so, I should wait more.
However, colonel Mark Tawnley, I am not wasting my time in this project. What were done during these last several weeks:

1. familiarization with the innards of my sample of the PST CaK. This inspection showed me that YG is in a LNIB condition.
All other filters are sick for rusting. Still barely useable PST as is.

2. Read a lot about this mod type and now no unclear questions remains.

3. Found Bob's Yoesle design sketch of how to make a sealed chamber for the YG - to protect it against possibly environmental attacks. Will make such a chamber later. Also, saw the simplest rig by Bob, for CaK mod with Baader CCD blue-violet filter as an ERF. Will do the same no, but with two Hoya 80A filters as the ERF.

4. Revised my refractor scopes collection and found 90mm F/10, 100mm F/10 achromats as the first candidates for my first stage mod CaK.
Then a 6" F/5 or a 6" F/8 achromat will be the donor for my CaK mod stage 2.

5. Ordered three filters for an ERF. 77mm - for internal ERF in 6" refractor, 50mm - for 100mm refractor.

6. Will do the test of internal ERFs - many hours straight being pointed at the sun (no YG installed, only ERF).

7. Bought a used (lightly) Baader Solar Hershel Wedge - as the ERF for using CaK mod with larger telescopes (C11 and C14). Already test it in it's native white light mode. Works just fine.


Valery.
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Re: My PST CaK mod. Help!

Post by marktownley »

Good progress Valery, I look forward to seeing how it all develops :)


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Re: My PST CaK mod. Help!

Post by swisswalter »

Valery wrote: 4. Revised my refractor scopes collection and found 90mm F/10, 100mm F/10 achromats as the first candidates for my first stage mod CaK.
Then a 6" F/5 or a 6" F/8 achromat will be the donor for my CaK mod stage 2.

.


Hi Valery

a very good choice. I found too that my simple 127/1200 fraunhofer works best for CaK work


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