Tuning of Quark?

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Re: Tuning of Quark?

Post by christian viladrich »

Hello Minh,
It's nice to have you on board. I am sure you will have great views of the Sun from Vietnam. And this will complete the longitude coverage of the Sun by Solar Chat observers :-)
Here are some elements regarding your questions.

1) Regarding tilt in front of the Quark :

If the tilt is between the etalon and the telecentric, you will correct the issue with the center wavelength, but you will increase the FWHM depending on the amount of tilt. In this figure X is the tilt angle :
http://astrosurf.com/viladrich/astro/in ... -angle.JPG

if the tilt is in front of the telecentric, then there is no increase of the FWHM (good news), but no change of the CWL (bad news). So it does not change the issue you are facing.

Before the Quark came the Ion. Depending on the ambient temperature, the Ion could also have some issue reaching reference temperature. The cooling system (Peltier + fans) was a bit undersized.
Years ago, I used a big CCD camera for solar imaging. The camera was cooled by water circulation. It was very effective.
I don't know if you can try something like this with the Quark ? Or try convincing DayStar to make more powerfull cooling system ?


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Re: Tuning of Quark?

Post by christian viladrich »

2) Regarding FWHM as a function of f-ratio:
Optics are optics. There is no magic in it. The references are provided on my website:
http://astrosurf.com/viladrich/astro/in ... P-math.htm

Here is a comparison between images taken at f/27 and f/35 and a 0.3 A etalon :

http://astrosurf.com/viladrich/astro/so ... 03A-C8.jpg

http://astrosurf.com/viladrich/astro/so ... C8-F35.jpg

Indeed, quality of an etalon is not only about FWHM but also about uniformity of FWHM and CWL accross the etalon. For example, a FWHM of 0.3 A is meaning less if you have a drift of CWL of 0.6A accros the field.

Air-spaced etalon can now be tested by willing amateurs. See the related various posts on Solar Chat and also :
http://astrosurf.com/viladrich/astro/in ... sting.html

Testing of mica-spaced etalon is in the pipeline ;-) I hope to have some results during summer. Meanwhile, here is a very interesting paper including results here :
https://www.researchgate.net/publicatio ... XAMINATION


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Re: Tuning of Quark?

Post by christian viladrich »

3) Regarding 8-bit versus 16-bits.
For "usual" solar imaging, I never have found any difference. The only difference I have found is for solar eclipses or high dynamic range object like this:
http://astrosurf.com/viladrich/astro/te ... ndree.html

Still, I recently came onto something very much unexpected with the ASI 1600. In 8-bit acquisition, there is big difference in dynamic and S/N between the "fast" and "slow" modes of acquisition. This is as if the dynamic range is cut down in the "fast" mode. Indeed, the exposure time leading to image saturation is longer in the "slow" mode. The ASI 290 does not behave like this, nor the Basler 1920-155.


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Re: Tuning of Quark?

Post by christian viladrich »

4) Regarding BW versus color senor:
This is true you can use binning during acquisition. For full disk imaging, there is no issue. For high-resolution imaging, you could face a lack of light (since only one out of four pixels actually see Ha). Still, there is plenty you can do with your camera.


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Re: Tuning of Quark?

Post by minhlead »

marktownley wrote: Sun May 16, 2021 9:03 am
minhlead wrote: Sun May 16, 2021 7:56 am
So the question is: what is more likely to be the fact here?
What Christian has on his website is fact.
I know, i am operating on the assumption that his calculation are correct. What I am asking was "Is DS over stated their specs or their filter is actually have way lower bandpass that we can benefit from by stopping down futher than f/30?"


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Re: Tuning of Quark?

Post by minhlead »

christian viladrich wrote: Sun May 16, 2021 12:11 pm Hello Minh,
It's nice to have you on board. I am sure you will have great views of the Sun from Vietnam. And this will complete the longitude coverage of the Sun by Solar Chat observers :-)
Here are some elements regarding your questions.

1) Regarding tilt in front of the Quark :

If the tilt is between the etalon and the telecentric, you will correct the issue with the center wavelength, but you will increase the FWHM depending on the amount of tilt. In this figure X is the tilt angle :
http://astrosurf.com/viladrich/astro/in ... -angle.JPG

if the tilt is in front of the telecentric, then there is no increase of the FWHM (good news), but no change of the CWL (bad news). So it does not change the issue you are facing.

Before the Quark came the Ion. Depending on the ambient temperature, the Ion could also have some issue reaching reference temperature. The cooling system (Peltier + fans) was a bit undersized.
Years ago, I used a big CCD camera for solar imaging. The camera was cooled by water circulation. It was very effective.
I don't know if you can try something like this with the Quark ? Or try convincing DayStar to make more powerfull cooling system ?
Cannot seems to thank you enough for your answers, Christian. Exactly what I was looking for.
Just a quick question.
You said if the tilt is introduce in front of the telecentric barlow then there is no gain/loss in CWL or FWHM. But Daystar mentioned about focuser droop affects the CWL and the Quark must be temperature tuned to compensate for the CWL shift which suggests that a tilt in front of the telecentric (tilt of the whole Quark unit) will shift the CWL blue regardless of the direction of the tilt.
This is what confuses me. Could you please elaborate further? Also, my Quark is the newer model with unremovable barlow so i do not have the option of introducing the tilt between the telecentric barlow and the etalon.
Again, thanks


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Re: Tuning of Quark?

Post by minhlead »

christian viladrich wrote: Sun May 16, 2021 12:44 pm 4) Regarding BW versus color senor:
This is true you can use binning during acquisition. For full disk imaging, there is no issue. For high-resolution imaging, you could face a lack of light (since only one out of four pixels actually see Ha). Still, there is plenty you can do with your camera.
Actually in most OSC binning there are a mono mode where the intensity of the binned pixel is determined from the total intensity of all 4 pixels in the cfa then quadruped so the intensity of the binned pixel is almost 4x the brightess pixels. There are some loss due to transmission of the CFA but I find it works quite well overal, never ran into lack of light (I shot most of my images at 3ms at unity gain which is slower than many mono camera but useable I think.)


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Re: Tuning of Quark?

Post by minhlead »

christian viladrich wrote: Sun May 16, 2021 12:29 pm 2) Regarding FWHM as a function of f-ratio:
Optics are optics. There is no magic in it. The references are provided on my website:
http://astrosurf.com/viladrich/astro/in ... P-math.htm

Here is a comparison between images taken at f/27 and f/35 and a 0.3 A etalon :

http://astrosurf.com/viladrich/astro/so ... 03A-C8.jpg

http://astrosurf.com/viladrich/astro/so ... C8-F35.jpg

Indeed, quality of an etalon is not only about FWHM but also about uniformity of FWHM and CWL accross the etalon. For example, a FWHM of 0.3 A is meaning less if you have a drift of CWL of 0.6A accros the field.

Air-spaced etalon can now be tested by willing amateurs. See the related various posts on Solar Chat and also :
http://astrosurf.com/viladrich/astro/in ... sting.html

Testing of mica-spaced etalon is in the pipeline ;-) I hope to have some results during summer. Meanwhile, here is a very interesting paper including results here :
https://www.researchgate.net/publicatio ... XAMINATION
May I suggest a simpler setup to test the uniformity of the Quark:
I posted it in Stargazerlpunge but have no response there.
https://stargazerslounge.com/topic/3737 ... nt-4060882
In short, just get a small white LED (my phone's flash light works fine) , put it in front of the scope with the Quark and camera in place , shinning down the OTA and take an exposure (I took mine at 60s) . All the deformity/mica sheet cleave error/ dust spot will shows in the resulting photo.
Here is mine. The result looks bad with plenty of dust spots /mica cleaving scratches. But mine performs okay under the sun (not very uniform but flats does help.
Screenshot_20210314-133820_TeamViewer~2.jpg
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Re: Tuning of Quark?

Post by christian viladrich »

Hello Minh,
Regarding your test, it is not sensitive to change in CWL since your source of light is "broad band". In other words, if there is no change of FWHM, but only a change of CWL you will have an uniform image (if there is no local change in peak transmission of course).
On top of that, if your camera is not focused on the etalon surface, you won't be able to see the etalon small size effects (inclusions, cleavage defaults, etc).
You can improve on this by using an Ha lamp and a collimated beam, and using a camera focused on the etalon surface:
http://astrosurf.com/viladrich/astro/in ... 94-410.jpg
Still, this type of test is difficult to interpret in terms of CWL and FWHM uniformity.


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Re: Tuning of Quark?

Post by christian viladrich »

minhlead wrote: Sun May 16, 2021 3:21 pm
You said if the tilt is introduce in front of the telecentric barlow then there is no gain/loss in CWL or FWHM. But Daystar mentioned about focuser droop affects the CWL
Can you give me a link to the web page they say so ?


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Re: Tuning of Quark?

Post by minhlead »

christian viladrich wrote: Sun May 16, 2021 4:30 pm
minhlead wrote: Sun May 16, 2021 3:21 pm
You said if the tilt is introduce in front of the telecentric barlow then there is no gain/loss in CWL or FWHM. But Daystar mentioned about focuser droop affects the CWL
Can you give me a link to the web page they say so ?
http://www.daystarfilters.com/downloads/QuarkManual.pdf
It's in the page 3 of the Quark' s Manual
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Re: Tuning of Quark?

Post by minhlead »

christian viladrich wrote: Sun May 16, 2021 4:30 pm
minhlead wrote: Sun May 16, 2021 3:21 pm
You said if the tilt is introduce in front of the telecentric barlow then there is no gain/loss in CWL or FWHM. But Daystar mentioned about focuser droop affects the CWL
Can you give me a link to the web page they say so ?
So I've completed a tec cooler for the Quark, hoping to bring it down a few degrees below 30 and see if the CWL shift blue. Only if the clouds just go away


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Re: Tuning of Quark?

Post by minhlead »

christian viladrich wrote: Sun May 16, 2021 4:30 pm
minhlead wrote: Sun May 16, 2021 3:21 pm
You said if the tilt is introduce in front of the telecentric barlow then there is no gain/loss in CWL or FWHM. But Daystar mentioned about focuser droop affects the CWL
Can you give me a link to the web page they say so ?
Okay so I found a video of Jen at DS expalining the tuning process in more detail including what happens if you tilt the etalon.
https://youtu.be/L_tq1KA_QEA
(The part regading tilting is at 45:00 and 52:00)
And judging by the look of the spectrometer on the video, it seems tilting the etalon does not affect the FWHM much, the peak still seems pretty much as narrows after tilting to me.


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Re: Tuning of Quark?

Post by christian viladrich »

minhlead wrote: Wed May 19, 2021 5:27 am And judging by the look of the spectrometer on the video, it seems tilting the etalon does not affect the FWHM much, the peak still seems pretty much as narrows after tilting to me.
I give you a hint Minh ;-)
You can see several "teeth" of transmission on the screen. So it is only the etalon which is measured there, and not the whole unit (telecentric, ITF, BF, etalon).


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Re: Tuning of Quark?

Post by minhlead »

christian viladrich wrote: Thu May 20, 2021 6:10 pm
minhlead wrote: Wed May 19, 2021 5:27 am And judging by the look of the spectrometer on the video, it seems tilting the etalon does not affect the FWHM much, the peak still seems pretty much as narrows after tilting to me.
I give you a hint Minh ;-)
You can see several "teeth" of transmission on the screen. So it is only the etalon which is measured there, and not the whole unit (telecentric, ITF, BF, etalon).
I do aware of that. But the way Jen put it seems to suggest if the whole Quark (including the barlow and the etalon) tilts then the cwl will shift blue, just like when you tilt the etalon alone (minus the other "teeth" since they filtered out by the trimming filter).


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Re: Tuning of Quark?

Post by minhlead »

Montana wrote: Thu May 06, 2021 5:10 pm Mmm that's a tough one. If I was just looking at the first I would say -3 or -2 looks best and would be interesting to see further on the scale. Looking at the bottom set, they all don't look that great ;) all look off band to me. Weird!
I would definitely do the whole scale.

Alexandra
christian viladrich wrote: Thu May 20, 2021 6:10 pm
minhlead wrote: Wed May 19, 2021 5:27 am And judging by the look of the spectrometer on the video, it seems tilting the etalon does not affect the FWHM much, the peak still seems pretty much as narrows after tilting to me.
I give you a hint Minh ;-)
You can see several "teeth" of transmission on the screen. So it is only the etalon which is measured there, and not the whole unit (telecentric, ITF, BF, etalon).
Alright,so tilting the whole Quark definitely shift the CWL.
I tilt the Quark and everything behind it with a field tilter about 1 degree and now the best setting no longer -5 but jump a few knobs to -3 or -2. (The 0 or -1 setting now have the best field uniformity but the local contrast is best with -3 or -2 setting.)
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Re: Tuning of Quark?

Post by marktownley »

You're doing some great experimentation here Minh, and getting some effective results.


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Re: Tuning of Quark?

Post by minhlead »

marktownley wrote: Sat May 22, 2021 9:55 am You're doing some great experimentation here Minh, and getting some effective results.
Thanks mark.


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Re: Tuning of Quark?

Post by rsfoto »

Hi,

The best result for me judging from my limited experience is -3


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Re: Tuning of Quark?

Post by minhlead »

rsfoto wrote: Sat May 22, 2021 3:50 pm Hi,

The best result for me judging from my limited experience is -3
same here :)) Completely newbie.


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Re: Tuning of Quark?

Post by Valery »

If the bottom images represent the full FOV, then the best new position is -5 or -4 and you just need to use a ROI (region of interest) and use this upper half of the field of view.
In general, uniformity wise this Quark is quite poor. It has a narrow enough bandwidth, but a huge gradiend of the central wave length position (poor CWL uniformity). If the size of this maximal ROI is OK for you, then use this Quark. If you want to use at least 80-90% of the FOV, then you should try to find a better Quark sample.

Sorry to tell you this fact (as this seen from your images), but better to know the truth.


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Re: Tuning of Quark?

Post by Valery »

Here you can see your screen shot at -5 with ROI indicated, then this ROI as a crop and the ROI image corrected for a field brightness non-uniformity.

At least you can move ahead. If you will use less reduction after the Quark and prior to the camera, the ROI will be larger on the camera chip.

Hope this helps.


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Re: Tuning of Quark?

Post by minhlead »

Valery wrote: Sat May 22, 2021 7:21 pm Here you can see your screen shot at -5 with ROI indicated, then this ROI as a crop and the ROI image corrected for a field brightness non-uniformity.

At least you can move ahead. If you will use less reduction after the Quark and prior to the camera, the ROI will be larger on the camera chip.

Hope this helps.


Valery
Excellent explaination, Valery. I do understand that my Quark have poor field uniformity, that's no secret the first time I look through the eyepiece, the "sweet band" effect is apparent on large fov. Unfortunately I am from VN and returning the Quark for a better one simply out of the question so I have to find a way to make it work with what I get. Luckily I am mostly an imaging guy and spend very little time doing visual so there are some trick that can be done.
I am using ROI to crop out the out of band exactly like your illustration, it's help speed up the frame rate a lot too (I am using a color camera at bin 2x2 so a full chip readout only gave me 16 or so fps, after cropping it's 30fps which is somewhat acceptable) and since the sensor is relatively large (M4/3) the FOV after cropping still about 30% larger than if I am using a mono camera with a 1/1,2 inches sensor like the IMX174 which I think is acceptable. And I've done some good images with this Quark so I think I'll keep it.
To my layman's eyes I find the -4 -5 setting seems to lack some local contrast in comparing with the -3, -2 settings, the filaments seems to be fainter in -4, -5 and surface features also less pronounced in -5. I am using -3 with cropping and flat calibration and some post processing trick to improve the field uniformity and the result is okay so far. But I'll surely try -5 per your advices. Thanks you for your time and helpful advices, Valery.
Last edited by minhlead on Sun May 23, 2021 3:44 am, edited 1 time in total.


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Quark Chromosphere Doublestacked with PST etalon
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DeepSolar64
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Re: Tuning of Quark?

Post by DeepSolar64 »

Hello Minh,
It's nice to have you on board. I am sure you will have great views of the Sun from Vietnam. And this will complete the longitude coverage of the Sun by Solar Chat observers :-) _ Christian Viladritch

We now have better solar coverage than the GONG network and lately have been more reliable! :band

James


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Re: Tuning of Quark?

Post by Montana »

My pick would be -4, but -3 is OK :)

Alexandra


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Re: Tuning of Quark?

Post by christian viladrich »

Hello Minh,
Finally there is inded some impact of the telecentric tilt on CWL and FWHM. Still, the impact is smaller that if the etalon alone was tilted (and the telecentric and the telescope shared the same optical axis).
See Zeemax and Oslo simulations there :
viewtopic.php?f=4&t=32038


Christian Viladrich
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
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