Daystar Quark - Help in determining "on band" operation

[Fabio_Imm]

Hello,
As suggested by a number of members of the forum, today I invested 3.5 hours to test almost all the settings of the adjustment knob of my Daystar quark.
All the images were obtained by stacking 25% of the best shots in a 1k frame .ser file; exposure 10 ms, focus unchanged, took a flat field for each individual setting placing cellophane on the scope aperture. Minimal post processing, identical for all the shots.
After each click adjustment I let the unit to stabilize (solid green light).
Sky transparency was very good, seeing conditions were changing between the pictures.

The results of the assessment are summarized in the pdf file, in the same order of the experiment (from full CW to full CCW) the pictures are taken 20 min apart.
Since I find it difficult to identify "on-band operation", could you help me by giving your advice/opinion on them?

My particular unit seems to be completely off-band in the CW extremity of the adjustment range: images taken at +5 and +4 CW were total rubbish, therefore were discarded.
On my unit the useful range seems to be between -3CCW and -5CCW.
At -5CCW some bright spots start to appear: if those are EB, then at that setting it should be slightly off-band in the blue wing, but I cannot confirm it since there is no -6CCW setting (As Alexandra said )
Also, another conclusion is that the etalon units used in the SS60 have a broader bandwidth than those sold as standalone Quarks.

Cheers

Fabio

[rsfoto]

Hi Fabio,

For me -5CCW looks closest to be in band but also the processing would take care of more contrast.

Would you send me the -5CCW ser file and so I could see if there is more detail there ?

Apart from the 10 ms what is the camera brand, what where the Gain, gamma and brightness settings. This setting also influence the result.

You can send it via wetransfer or maybe upload to some cloud storage and pass on the link for download.

I had a QUARK but never really did get good details so I send it back and forgot about it. I bought it during a NEAF 2018 show and allegedly it was even handpicked by the owner Jen but never got anything out of it. I do not think it was the telescopes as I used a Takahashi TOA 130 or my little Takahashi FS-78.

regards Rainer

[Fabio_Imm]

Rainer, thank you for your help.
I'll set up a shared folder in Dropbox and PM you the link.
In the folder I'll include also the relevant acquisition settings.

Fabio

[marktownley]

Yes, -5CCW is the best in this instance.

[Montana]

I think -5 looks best for me but the key thing I noticed is DONT do a flat field in this kind of test as it makes the process easier. The key is to watch the on band area move across the field, it will be the area of darkest contrast. You can watch it move in and out of the field. You can see some examples here https://solarnutcase.livejournal.com/12257.html

Is it possible to process the same but without the flat field?

Alexandra

[Fabio_Imm]

Hi Alexandra,
Thank you for the explanation and the link to your blog post: now I better understand what to look for!
I'll re-process them without the flat field correction, maybe also lowering to 10% the of stacked frames... monday started with a lot of work .
As a side note, just for the sake of experimentation, I tried inserting a polarizing filter between the quark and the camera, adjusting it for maximum transmission: in my subjective opinion (but I can't explain why) that helped a lot viewtopic.php?f=4&t=29931.
The images in the post are flat-field corrected, but with the polarizing filter in place in the original pictures I clearly saw the upper left corner to be darker than the rest.
In all the previous pictures (w/o the polarizer) there was a faint multiple banding across the FOV: 3-4 light/dark stripes alternating, not Newton Rings.

Again, thank you for your help!

Cheers

Fabio

[Valery]

Hello,
As suggested by a number of members of the forum, today I invested 3.5 hours to test almost all the settings of the adjustment knob of my Daystar quark.
All the images were obtained by stacking 25% of the best shots in a 1k frame .ser file; exposure 10 ms, focus unchanged, took a flat field for each individual setting placing cellophane on the scope aperture. Minimal post processing, identical for all the shots.
After each click adjustment I let the unit to stabilize (solid green light).
Sky transparency was very good, seeing conditions were changing between the pictures.

The results of the assessment are summarized in the pdf file, in the same order of the experiment (from full CW to full CCW) the pictures are taken 20 min apart.
Since I find it difficult to identify "on-band operation", could you help me by giving your advice/opinion on them?

My particular unit seems to be completely off-band in the CW extremity of the adjustment range: images taken at +5 and +4 CW were total rubbish, therefore were discarded.
On my unit the useful range seems to be between -3CCW and -5CCW.
At -5CCW some bright spots start to appear: if those are EB, then at that setting it should be slightly off-band in the blue wing, but I cannot confirm it since there is no -6CCW setting (As Alexandra said )
Also, another conclusion is that the etalon units used in the SS60 have a broader bandwidth than those sold as standalone Quarks.

Cheers

Fabio

Fabio,

What is the F/D on the Quark etalon?


Valery

[Fabio_Imm]

Hi Valery,
The scope is a Celestron 80ED, native f/D is 7.5
With the 4.2X telecentric barlow embedded in the Quark, the etalon should work at around f/D=31.5

The Quark I am using was pulled out of a Daystar Solar Scout SS60

As a side note and to make a comparison, I ran the calculation in reverse for the stock Daystar Solar Scout SS60: with 930mm fl and 60mm D resulting in f/D=15 (very low) meaning that the lens of the SS60 has a native fl of 221mm with f/D=4... isn't it a bit too fast? or did I make a calculation mistake somewhere?

Cheers

Fabio

[Valery]

Hi Valery,
The scope is a Celestron 80ED, native f/D is 7.5
With the 4.2X telecentric barlow embedded in the Quark, the etalon should work at around f/D=31.5

The Quark I am using was pulled out of a Daystar Solar Scout SS60

As a side note and to make a comparison, I ran the calculation in reverse for the stock Daystar Solar Scout SS60: with 930mm fl and 60mm D resulting in f/D=15 (very low) meaning that the lens of the SS60 has a native fl of 221mm with f/D=4... isn't it a bit too fast? or did I make a calculation mistake somewhere?

Cheers

Fabio

No formal mistake were here. The only "mistake" is that this given Quark was optimized to work at F/17 or so. In this case it's best position for a CWL should be around 0. To move your best CWL position with a given Quark at least to -4 CCW, you need to use a bit faster F/D at the Quark etalon, say F/25-26.
So, use a telescope with a native F/6. Then see where your Quark gives the most contrast picture - at -5, at -4 or at -3 ?
Then make several paper round stops of the aperture and use a F/6.2, F/6.5, F/6.7 and see where the most contarst image will be with each of these stops. May be will be at -4CCW. Then see with which stop the best contrast will be at -5CCW for sure.
May be your present F/D is a real optimum at -5CCW, but you can be sure. May be a little more fast system, say, F/28 will give a better contrast at -5CCW.

I hope you got the idea.

Valery

[Fabio_Imm]

No formal mistake were here. The only "mistake" is that this given Quark was optimized to work at F/17 or so. In this case it's best position for a CWL should be around 0. To move your best CWL position with a given Quark at least to -4 CCW, you need to use a bit faster F/D at the Quark etalon, say F/25-26.
So, use a telescope with a native F/6. Then see where your Quark gives the most contrast picture - at -5, at -4 or at -3 ?
Then make several paper round stops of the aperture and use a F/6.2, F/6.5, F/6.7 and see where the most contarst image will be with each of these stops. May be will be at -4CCW. Then see with which stop the best contrast will be at -5CCW for sure.
May be your present F/D is a real optimum at -5CCW, but you can be sure. May be a little more fast system, say, F/28 will give a better contrast at -5CCW.

I hope you got the idea.

Valery

Hi Valery,
I see what you mean.
Unfortunately I have no faster f ratio refractors at hand.
Maybe I'll return the etalon to the original SS60 scope and experiment on it with aperture stops, as you suggested.
My etalon seems to like to run "colder", since even in the SS60 the best contrast was obtained with -3 -4 CCW settings.


Cheers

Fabio