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Re: PST Etalon with a Quark, Log & Results

Posted: Mon Jan 21, 2019 5:04 pm
by MalVeauX
Yea, I'm sure I'm aggravating the limb with processing. I'm trying different approaches to see if anything can work without blasting the double limb as bad.

I agree I'm probably still not perfectly tuned on band. It's hard to know where I am with the tuning since there's no guarantee what any particular setting is on either etalon. And the number of combinations of each setting on the Quark versus the PST etalon is a significant number to test. Basically I need to just put my Quark on a setting, then slowly tune through the PST etalon and see real time what happens on the limb. I need some long sessions for this, the weather has not been playing nice.

Hopefully I can test this soon!

Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Tue Jan 22, 2019 10:06 pm
by Bob Yoesle
One thing I do notice is that depending on the processing I can "pull" the double edge out of almost any image...
Hi Ken,

For me it was a long learning curve to discover exactly what an on-band image should look like. I still have trouble at times, especially in the typical relatively poor seeing I have, to take the time needed to perfectly tune two etalons, which seems at least 4-6 times more difficult than tuning a single etalon. Perhaps more significantly, in my experience consumer H alpha etalon quality in the past few years seems to have decreased due to needing to make etalons more affordably.

Added to this - at least for my air-spaced etalons - is that changes in barometric pressure and temperature can have subtle but detectable changes in the CWL of the filter system. So while I may start pretty close to exactly on-band, later I may need to make some fine adjustments to optimize the tuning due to these pressure and temperature changes, which can effect both the refractive index of the etalon gap, and change the spacing of the etalon plates themselves via spacer expansion and contraction.

This might be one area where the solid-spaced temperature tuned etalons may prove a little more stable under changing atmospheric conditions. The downside is the lag time in making tuning changes, and perhaps the accuracy of the temperature setting reflected in the wavelength display (if present). On the other hand, I don't really know how sophisticated the temperature regulation of these etalons is, and what if any changing thermal related gap spacing might result in over time.

See if you can pull the double limb out of one or more of these images. They are some of my better unprocessed and minimally compressed jpeg conversions of the 900 mm and 1800 mm FL tiff files out of Registax, using double stacked pre-Meade SM90 etalons:

Re: PST Etalon with a Quark, Log & Results

Posted: Wed Jan 23, 2019 12:36 pm
by marktownley
Those double stack 90s are sublime Bob. Very Jealous!

Re: PST Etalon with a Quark, Log & Results

Posted: Wed Jan 23, 2019 2:07 pm
by Bob Yoesle
Thanks Mark - I was lucky to be able to get these etalons when such quality was available and still relatively affordable.

I should note that the above images were wavelet processed in RegiStax6, but had no additional post processing, and the their RG630 ERF's were replaced by a single Baader DERF for improved IR rejection and image brightness.

Re: PST Etalon with a Quark, Log & Results

Posted: Wed Jan 23, 2019 3:14 pm
by bart1805
Wow, they look way better than all of my processed images. So agree with Mark: jealous!
About the double limb. If there is no double limb visible in the images it is not possible (in my opinion) to make it visible. It simply is not there.
But if you have an image of a normal single stacked etalon, you see the double limb. And if you proces "hard", use a lot of contrast and gamma for example, you can make it disappear. Off course it is still there, but not visible in the processed image. I personally don't really like these kind of images, but that is just a matter of taste.

Re: PST Etalon with a Quark, Log & Results

Posted: Wed Jan 23, 2019 7:28 pm
by MalVeauX
Heya,

Played around with tuning today a little. Had a chance to see if I could do some tests between clouds, which I was lucky to have some decent seeing and some finally fairly good weather and a nice new sunspot has evolved, so a great way to test tuning. I can't seem to eliminate the double limb. However, I can definitely see differences in the tuning with respect to sunspots, where the double stack removes more of the umbra, and in the single stack the umbra are very visible and dark. Quite interesting.

Single stack (Quark only):

Image

Image

Double Stack (Quark & PST Etalon):

Image

Image

And here's a double stack of the filament and proms (the limb is worse compared to before):

Image

++++++++++++++++++++++
++++++++++++++++++++++

Here's a limb + prom + new AR example, unprocessed other than stacking and a little histogram/level adjustment to see the limb:
Limb_Example.jpg
Limb_Example.jpg (123.75 KiB) Viewed 8305 times
Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Wed Jan 23, 2019 9:04 pm
by marktownley
The limb shot is excellent Marty. Don't worry about the ghost / residual of the double limb; with the etalons you have you are on peak performance. The only way you are going to improve is by doing what Valery does and try many etalons and cherry pick the best. There's nothing wrong with the images you are getting.

Re: PST Etalon with a Quark, Log & Results

Posted: Fri Jan 25, 2019 4:46 pm
by MalVeauX
Another go at AR2733 with the Quark & PST Etalon tuning testing.

Here's the limb & prom (Quark & PST etalon):

Image

Image

Here's AR2733 with just the Quark (visible umbra):

Image

Image

Here's AR2733 with the Quark & PST etalon (umbra are no longer visible):

Image

Image

Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Fri Jan 25, 2019 11:04 pm
by MapleRidge
Hi Marty...

These recent additions look great, especially the structures in the faint prom.

Well done :bow

Brian

Re: PST Etalon with a Quark, Log & Results

Posted: Mon Jan 28, 2019 6:48 pm
by MalVeauX
Heya,

Tested some more today with the Quark & PST Etalon.

Image

Image

Image

Image

Image

Image

Image

Image

Image

Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Mon Jan 28, 2019 11:30 pm
by MapleRidge
Marty...

These latest images look great!!!

Brian

Re: PST Etalon with a Quark, Log & Results

Posted: Tue Jan 29, 2019 5:08 pm
by MalVeauX
More from today with AR2733 & the double stack:

Image

Image

Image

Image

Image

Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Tue Jan 29, 2019 5:25 pm
by Bob Yoesle
Now you're cooking Marty! Pretty much right on band to me. The normally processed greyscale bright and dark mottles look exactly as they should, and there is no discernable double limb.

Re: PST Etalon with a Quark, Log & Results

Posted: Tue Jan 29, 2019 9:28 pm
by MalVeauX
Thanks, :bow

I've marked on the two etalons where to orient them for consistency. I still tweak here and there, but ultimately it seems to be best at this position.

The above were at 10ms exposure time, no gamma (neutral) and gain is running 160 to 200 for these, filling histogram into the 60~70% range.

Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Tue Jan 29, 2019 9:55 pm
by Astrophil
Marty, those are really really great images. You have that system working well. Congrats.

Phil

Re: PST Etalon with a Quark, Log & Results

Posted: Tue Jan 29, 2019 10:04 pm
by MalVeauX
Thanks Phil,

I have the C8 Edge & 214mm tri-band ERF. Just waiting for the filter holding cell to arrive from Germany.

This system will then transfer to that new setup. I will probably try it reversed with the PST etalon with its collimating lenses in the F10 beam of the C8 and then the Quark after, to maybe do a better job (with the blocking filter being last and likely more ideal I would think?).

Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Tue Jan 29, 2019 10:05 pm
by marktownley
I think you will do well with the edge HD, your seeing is better than mine.

Re: PST Etalon with a Quark, Log & Results

Posted: Tue Jan 29, 2019 10:15 pm
by MalVeauX
Hoping so! I love my 6" refractor, but I'd like to use something a little bigger and something color-free for planets and night astrophotography. The big old achromat is great in narrowband, but it's not great for visual spectrum on bright subjects. Can't complain, this 6" telescope was $250!

Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Tue Jan 29, 2019 10:43 pm
by Valery
MalVeauX wrote: Tue Jan 29, 2019 10:04 pm Thanks Phil,

I have the C8 Edge & 214mm tri-band ERF. Just waiting for the filter holding cell to arrive from Germany.

This system will then transfer to that new setup. I will probably try it reversed with the PST etalon with its collimating lenses in the F10 beam of the C8 and then the Quark after, to maybe do a better job (with the blocking filter being last and likely more ideal I would think?).

Very best,
Hi Marty,

C8 Edge will not work properly with PST etalon in it's native confifuration. Back space of this telescope is less than required 200mm+

So, the best is to work as with 6" refractor: Quark Chromosphere will work at F/43 (very nice for narrow bandwidth) + 0,6x reducer + IMX174 camera. You can add PST etalon naked (no it's native lenses).

Good luck.

Valery

Re: PST Etalon with a Quark, Log & Results

Posted: Tue Jan 29, 2019 10:45 pm
by Valery
MalVeauX wrote: Tue Jan 29, 2019 10:15 pm Hoping so! I love my 6" refractor, but I'd like to use something a little bigger and something color-free for planets and night astrophotography. The big old achromat is great in narrowband, but it's not great for visual spectrum on bright subjects. Can't complain, this 6" telescope was $250!

Very best,
I see you never looked through a 6" F/8 achromat + ARIES Chromacor-I or II ! They both are gamechangers in such a combination.


Valery

Re: PST Etalon with a Quark, Log & Results

Posted: Tue Jan 29, 2019 10:47 pm
by MalVeauX
Good to know Valery, thanks, so my configuration will remain as it is here when I move it over to the C8.

I'm sure a Chromacor would be nice. But, at the end of the day, the C8 Edge is more compact (less moment arm) than my huge refractor and has more resolution for imaging purposes.

Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Wed Jan 30, 2019 6:08 pm
by Astrophil
Marty, I'm sure you get the C8 working well. Looking forward to seeing your results.

Phil

Re: PST Etalon with a Quark, Log & Results

Posted: Fri Feb 08, 2019 4:36 pm
by MalVeauX
From this morning with the 150mm and the Quark & PST etalon:

Image

Image

Image

Image

Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Tue Feb 12, 2019 3:39 pm
by MalVeauX
Here's some RAW stacks with only histogram stretching and a little deconvolution via IMPPG from the previous data set with no other processing performed. This is the Quark + PST etalon. These are 180 frames stacked each (out of 2000).

prom_ds_crop_01.jpg
prom_ds_crop_01.jpg (89.86 KiB) Viewed 7903 times
prom_ds_crop_02.jpg
prom_ds_crop_02.jpg (114.24 KiB) Viewed 7903 times
Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Tue Feb 12, 2019 7:32 pm
by marktownley
Love these raw stacks Marty! But, then you can probably tell from the images I post I err on that side of things with my processing...

You have the etalon combination nailed!

Re: PST Etalon with a Quark, Log & Results

Posted: Tue Feb 12, 2019 10:52 pm
by MalVeauX
There are places where I can see a double-limb, others it's gone. It definitely can be made more apparent with different processing. I prefer a darker more contrasty surface, but it's difficult to do that without wrecking the limb with it. I wish it were easier to way under-example and simply lift proms and the limb, but due to the transmission levels, the amount of gain being used, this seems to not work for this particular setup, at least yet. It may be a processing thing on my end that I have to figure out.

Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Wed Feb 13, 2019 8:54 pm
by Bob Yoesle
Hi Marty,

In some of your most recent images I'm seeing just a hint of the double limb, which is not obtrusive. In others I'm seeing processing artifacts, not the double limb of the photosphere:

M Wise highlight.jpg
M Wise highlight.jpg (241.96 KiB) Viewed 8566 times

Note the irregular hard edge appearance all along the limb and at the indicated locations...
Love these raw stacks Marty! But, then you can probably tell from the images I post I err on that side of things with my processing...
Mark I don't think you are in "err." I've been thinking about this for awhile. Here's my thoughts on the subject.

I guess it comes down to what is the purpose of posting images on these forums to begin with. With all due respect to Alan Friedman (a very talented graphic artist by trade - https://avertedimagination.squarespace.com/), his introduction of using colorized inverted (negative) disc images and positive prominence images made for dramatic and colorful "artistic impressions," but do not look anything like the Sun. They also made single stacked images perhaps somewhat "better looking" without the discontinuity at the limb where limb darkening runs into the bright ring of chromosphere - likely their original purpose. This is essentially hiding an imaging system defect in order to present "pretty pictures." To me it seems a little unfortunate that the forums are now awash in this faux imagery, giving many beginners an untrue version of reality, and is at odds to some degree with the principles of scientific accuracy.

I'd compare what is seen so often to the equivalent posting pictures of your family (sometimes ad nauseum) on social media like this:

FamilyGalleryBW2.jpg
FamilyGalleryBW2.jpg (129.8 KiB) Viewed 8566 times

Or not to be sexist, but most of the folks on this forum are men. How many find one of the most beautiful of women to ever have walked the Earth attractive inverted and contrast enhanced, but with her eyes left normal?

Sophia.jpg
Sophia.jpg (265 KiB) Viewed 8566 times

Unless you're a fan of Andy Warhol, it doesn't do much for me. Not that occasionally an inverted or altered image isn't sometimes (sparingly) useful. From my perspective, the positive disc with negative prominences is instructive by demonstrating that prominences and the disc filaments are in reality one in the same phenomena, and that dark details on a light background are sometimes easier for the eye to perceive (I don't find this as true for the disc, if at all):

Filaproms full disc.jpg
Filaproms full disc.jpg (433.44 KiB) Viewed 8566 times

Off soapbox, thanks for looking, and of course your mileage - and opinion - may vary.

Re: PST Etalon with a Quark, Log & Results

Posted: Fri Feb 15, 2019 4:47 pm
by MalVeauX
Heya,

Rotten weather lately. I got to do some more tests. This time, I revisited doing a full disc with the Quark & PST Etalon. I must have totally missed the boat because I guess I never tried putting a 0.5x focal reducer on the standard 1.25" nose extension after the tilt adapter (effectively moving it farther away from the sensor) and inserting that into the Quark's eyepiece holder, but also tried it with the PST etalon with apdaters in place and a 2" to 1.25" adapter and it too worked. I was able to get a full disc FOV out of a ST80 refractor with both the Quark & PST etalon with the 0.5x focal reducer and the IMX174 sensor size. I've had this for so long and yet I guess I just never tried putting the reducer on that side of the insert, and always had it closer to the sensor. Well dur dur dur, now I can do full discs no problem with my wee ST80.

Full Disc Double Stack Imaging train left to right:

ASI174MM -> ZWO Tilt Adapter -> 1.25" Nose -> GSO 0.5x 1.25" Focal Reducer -> 2" to 1.25" adapter -> PST Etalon & Adapters -> Quark with 2" eyepiece holder -> 2" 35mm Extension -" 2" 80mm Extension (with 2" UV/IR block filter threaded on nose) -> GSO 2" Crayford focuser -> ST80 (400mm F5) -> Aperture Mask of 60mm (F6.67)
FullDisc_Quark_PST_DS_02152019.jpg
FullDisc_Quark_PST_DS_02152019.jpg (56.61 KiB) Viewed 8525 times
Here's the FOV, parameters, histogram and real time view in FireCapture:
ScreenShot_FullDisc_Quark_PST_DS_ST80_FR_02152019.jpg
ScreenShot_FullDisc_Quark_PST_DS_ST80_FR_02152019.jpg (139.52 KiB) Viewed 8525 times
Here's a processed result (from a single exposure, no gamma):

Image

Now, back to high res. Here's the 150mm with the Quark & PST Etalon as normal, with the IMX174 & 0.5x focal reducer.
SolarSetup_02152019.jpg
SolarSetup_02152019.jpg (57.18 KiB) Viewed 8525 times
Here's the parameters, histogram, flat field applied and real time view in FireCapture:
ScreenShot_HighRes_02152019.jpg
ScreenShot_HighRes_02152019.jpg (177.23 KiB) Viewed 8525 times
Here's today's filament & plage area near some limb prominences, I think I got the tuning better this time. Presented in normal view and inverted. This is the result of a single exposure, no gamma.

Image

Image

Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Fri Feb 15, 2019 6:19 pm
by marktownley
Looks good Marty!

Re: PST Etalon with a Quark, Log & Results

Posted: Sun Feb 17, 2019 5:08 pm
by MalVeauX
Had a little time this morning to get some testing between clouds.

150mm with the Quark & PST Etalon:

Image

Image

Image

Image

ST80 masked to 60mm with Quark & PST Etalon:

Image

Image

Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Thu Feb 21, 2019 6:28 pm
by MalVeauX
Managed a little full disc time this morning with the Quark & PST Etalon together:

Image

Image

Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Sun Feb 24, 2019 1:11 am
by MalVeauX
Heya,

I tried another setup today at two scales, full disc and a large scale. These are the Quark & PST Etalon together. One with the ST80 and one with a C8 Edge.

Image

Image

Image

Image

Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Wed Feb 27, 2019 4:43 pm
by MalVeauX
Here's the limb today with the Quark & PST etalon with respect to tuning out the double limb:

Image

Image

Image

Image

Earth Scale:
EarthScale01.jpg
EarthScale01.jpg (68.98 KiB) Viewed 8365 times
Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Wed Feb 27, 2019 6:15 pm
by MalVeauX
Toying around with some of the data to see what works best.

Here's one imaging run, 2000 frames, stacked 1250 of them. I've compared things from 60, 100, 180, 360, 500, 750, 1000, 1250, 1500, 2000 frames just to mess around with things. Playing around with different approaches to deconvolution and unsharp masking in IMPPG. For this one, it's lower on the deconvolution and harder on the unsharp mask. No other processing.
Unprocessed_1250frames_02272019.jpg
Unprocessed_1250frames_02272019.jpg (178.37 KiB) Viewed 8364 times
Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Fri Mar 01, 2019 9:34 pm
by MalVeauX
Does anyone know if a PST etalon can be stacked with a 2nd PST etalon without collimating lenses, like above, or do they both need to have their collimating lenses. Any ideas about the advantages with or without the 2nd set of collimating lenses?

I rarely see PST double stacks. I've seen a few here and there, they seem to be very fussy to get right. Curious if it would be worth trying a 2nd etalon since I already have one and adding a 10mm blocking filter.

Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Sat Mar 02, 2019 8:45 am
by marktownley
Try it, but I bet reflections will be a PITA...

Re: PST Etalon with a Quark, Log & Results

Posted: Sat Mar 02, 2019 8:57 am
by bart1805

Re: PST Etalon with a Quark, Log & Results

Posted: Sat Apr 20, 2019 11:31 pm
by MalVeauX
Heya,

Been a while, figured I'd update this. The transmission was pretty low, so it made larger imaging scales more difficult. So recently, just to re-visit this, I went to a smaller scale.

This is my ST80 (80mm F5) with full aperture, so the Quark results in an F21 beam. This is not ideal, however, it seems to be a better match for the IMX174 pixels and for mixing with the PST etalon. Not sure why. PST Etalon without the collimating lenses after that. ASI174MM inserted, without any focal reducer. Transmission was better, but still quite low. This is at 10ms, gain 155 (38%) and gamma was neutral (off). It was fairly noisy and had pronounced newtonian rings. I couldn't get a flat frame to save my life (even with a tilt adapter). Processed most of it away in post.

Anyhow, the limb seems pretty good. Maybe the best I've been able to tune together so far? I likely will not pursue this farther than this. I think as a small scale double-stack option, it's viable, but far from optimal. But, I figured I would stop here for now on this note, to show the limb and how things are going with this experiement.

This is from today, AR2739 coming up to the limb.
80mm_Quark_PSTetalon_DS_181frames_04202019.jpg
80mm_Quark_PSTetalon_DS_181frames_04202019.jpg (130.34 KiB) Viewed 8105 times
Solarsetup_05_04202019.jpg
Solarsetup_05_04202019.jpg (51.76 KiB) Viewed 8105 times
Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Sun Apr 21, 2019 7:29 pm
by Bob Yoesle
That's really very good Marty, and better than a lot of others I've seen with the more recently made filter systems.

Re: PST Etalon with a Quark, Log & Results

Posted: Sun Apr 21, 2019 8:01 pm
by MalVeauX
Bob Yoesle wrote: Sun Apr 21, 2019 7:29 pm That's really very good Marty, and better than a lot of others I've seen with the more recently made filter systems.
Thank Bob,

It's amazing how minute nudges on the etalon, rotation, and the difference it makes to have a F28 beam, F35 beam, F42 beam, and even F21 beams has on the end result. I'm not sure what the true difference is, but at F35~F42 I was never able to make it work, but at the looser F21 it works. I can't explain it. Maybe I'm missing something.

Unfortunately the transmission is just so low, but that may be copy variation on top of things.

I tested this morning to see differences in transmission with two sensors. I tested an IMX174 & IMX178 to see if binning and different quantum efficiencies might help. After calculations just for fun, I figured the IMX178 would be less "fast" for imaging, and in reality, it was. The larger pixels of the IMX174 are much faster. This morning, just binning 2x2, I was able to fill my histogram with this double stack at 10ms, 45 gain, no gamma. I could image with that. But, the under-sampling was severe and the limb was just a smear of pixels, so I abandoned that as an option.

I'll be comparing this to a Solarmax 60mm Double Stack maybe in the next week or so, to put the final nail in the coffin.

Very best,

Re: PST Etalon with a Quark, Log & Results

Posted: Tue Dec 14, 2021 12:51 am
by minhlead
MalVeauX wrote: Sun Apr 21, 2019 8:01 pm
Bob Yoesle wrote: Sun Apr 21, 2019 7:29 pm That's really very good Marty, and better than a lot of others I've seen with the more recently made filter systems.
Thank Bob,

It's amazing how minute nudges on the etalon, rotation, and the difference it makes to have a F28 beam, F35 beam, F42 beam, and even F21 beams has on the end result. I'm not sure what the true difference is, but at F35~F42 I was never able to make it work, but at the looser F21 it works. I can't explain it. Maybe I'm missing something.

Unfortunately the transmission is just so low, but that may be copy variation on top of things.

I tested this morning to see differences in transmission with two sensors. I tested an IMX174 & IMX178 to see if binning and different quantum efficiencies might help. After calculations just for fun, I figured the IMX178 would be less "fast" for imaging, and in reality, it was. The larger pixels of the IMX174 are much faster. This morning, just binning 2x2, I was able to fill my histogram with this double stack at 10ms, 45 gain, no gamma. I could image with that. But, the under-sampling was severe and the limb was just a smear of pixels, so I abandoned that as an option.

I'll be comparing this to a Solarmax 60mm Double Stack maybe in the next week or so, to put the final nail in the coffin.

Very best,
Wow I found this gems of a post hidden under mountains of content and thank you Marty for making such a detailed and meticulos log on your endeavour with the PST-Quark DS. This will be the lodestar for me on mine.
I have a few question before diving head first into this.
1. How do you rate this particular PST and Quark that you used on the mod (FWHM, sweetspot size ie. How big of a sweet spot did you get, say on a imx174 sensor?)
2. Did the sweet spot size of the PST increased in comparing with if you use in in the original scope? (I assume it would since it's in a telecentric beam with high F ratio but I am not sure)
3. How is you transmission loss compared to just the Quark (I see that you got 10ms exposure with the double stack but how much did you use before double stack?)
4. How did you tune the PST relative with the Quark (i can see you marked the rotation, did you use some kind of tilting mechanism on your PST? Did you aim for the darkest image possible or just tune it until highest contrast?
5. How is the reliability of the mod, after a long time use any problem arise?
Sorry for the many question and thanks again for your dedication!

Re: PST Etalon with a Quark, Log & Results

Posted: Wed Dec 15, 2021 6:34 am
by marktownley
minhlead wrote: Tue Dec 14, 2021 12:51 am Wow I found this gems of a post hidden under mountains of content and thank you Marty for making such a detailed and meticulos log on your endeavour with the PST-Quark DS. This will be the lodestar for me on mine.
I have a few question before diving head first into this.
1. How do you rate this particular PST and Quark that you used on the mod (FWHM, sweetspot size ie. How big of a sweet spot did you get, say on a imx174 sensor?)
2. Did the sweet spot size of the PST increased in comparing with if you use in in the original scope? (I assume it would since it's in a telecentric beam with high F ratio but I am not sure)
3. How is you transmission loss compared to just the Quark (I see that you got 10ms exposure with the double stack but how much did you use before double stack?)
4. How did you tune the PST relative with the Quark (i can see you marked the rotation, did you use some kind of tilting mechanism on your PST? Did you aim for the darkest image possible or just tune it until highest contrast?
5. How is the reliability of the mod, after a long time use any problem arise?
Sorry for the many question and thanks again for your dedication!
Hi Minh,

Sweetspot only exists in a collimated beam, it's size is a function of aperture size versus etalon size. The bigger the objective relative to etalon, the
smaller the sweetspot. Bigger sweetspot is preferable. The bigger the chip on the camera the more the region out of the sweetspot it will show, so, cropping / ROI may be the way to go.

To tune the PST etalon you just turn the knurled ring as you would normally. My experience is that tuning the etalon imparts some tilt as if the tuning is too extreme (in this configuration) you get a band, trick is to get the band central so that it covers the fov. I just tuned for the darkest filaments and avoided off band features.

I've been doing this for several years now and there are no reliability issues.

Mark

Re: PST Etalon with a Quark, Log & Results

Posted: Wed Dec 15, 2021 9:48 am
by christian viladrich
Hi Minh,
As an additional information, in a collimated beam the problem is non uniformity of the etalons (the sweet spot formation is only in collimiated beam). It might be that each of the two etalons are good as a single stack, but not good as a double stack because non uniformity of the CWL goes in different directions.
The only way to know is to try it ...

Re: PST Etalon with a Quark, Log & Results

Posted: Wed Dec 15, 2021 11:30 am
by minhlead
Great informations, thanks Mark and Christian.
@Christian: if that happens can I solve it by rotating the 2 etalon relative with each other and find a spot that have the un-uniformities matched?

Re: PST Etalon with a Quark, Log & Results

Posted: Wed Dec 15, 2021 12:17 pm
by christian viladrich
minhlead wrote: Wed Dec 15, 2021 11:30 am Great informations, thanks Mark and Christian.
@Christian: if that happens can I solve it by rotating the 2 etalon relative with each other and find a spot that have the un-uniformities matched?
Indeed, this is part of the tuning. Then you will find out if the result is good enough or not.
For example, I stacked a Quantum 0.6A with two different PST (only one at a time). One double stack combination was acceptable, the other very bad (because of non uniformity).

Re: PST Etalon with a Quark, Log & Results

Posted: Wed Dec 15, 2021 5:25 pm
by rsfoto
MalVeauX wrote: Sun Apr 21, 2019 8:01 pm
Bob Yoesle wrote: Sun Apr 21, 2019 7:29 pm That's really very good Marty, and better than a lot of others I've seen with the more recently made filter systems.
Thank Bob,

It's amazing how minute nudges on the etalon, rotation, and the difference it makes to have a F28 beam, F35 beam, F42 beam, and even F21 beams has on the end result. I'm not sure what the true difference is, but at F35~F42 I was never able to make it work, but at the looser F21 it works. I can't explain it. Maybe I'm missing something.

Unfortunately the transmission is just so low, but that may be copy variation on top of things.

I tested this morning to see differences in transmission with two sensors. I tested an IMX174 & IMX178 to see if binning and different quantum efficiencies might help. After calculations just for fun, I figured the IMX178 would be less "fast" for imaging, and in reality, it was. The larger pixels of the IMX174 are much faster. This morning, just binning 2x2, I was able to fill my histogram with this double stack at 10ms, 45 gain, no gamma. I could image with that. But, the under-sampling was severe and the limb was just a smear of pixels, so I abandoned that as an option.

I'll be comparing this to a Solarmax 60mm Double Stack maybe in the next week or so, to put the final nail in the coffin.

Very best,
Hi Marty,
... It's amazing how minute nudges on the etalon ...
Good that you mention it. As you perhaps know I have a stepper motor for changing the angle of my double stacked SM60 etalon. In order to move the a full turn of the lead screw I need to make 5120 steps having a pitch of 0.794 mm, it is a 32tpi threaded screw #6-32 UNC

I have seen that moving just 64 steps I already see a change of the sweet spot position. One step in my setup is a movement of 0.155 micron or better said 0.000155 mm which means I only move 64 x 0.155 for a change ...

Just a side note from my part :)