Uneven image with a replacement Quark

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cmas
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Uneven image with a replacement Quark

Post by cmas » Sat May 06, 2017 6:27 pm

Hey,

I thought I'd ask this also here. This is my second Quark Chromosphere unit - the first went back to Daystar as it was flexing from the frame (the image train was not aligned anymore) and also had some issues with uneven image despite extensive tuning with a tilt adapter and using flats, of course.

Well, today I tried to test my second Quark. Unfortunately due to the clouds I could not achieve comprehensive testing (run out of power in the field due to clouds and increased waiting time between acquisitions), but I started with the knob turned all the way clockwise (setting -5 on my notation) and coming there counter clockwise and ended up in +1 (while +5 would have covered all the settings).

The image train includes the following:
- 90 mm Baader D-ERF
- 80/480 mm TS FPL53 apo
- TS 2" to T2 adapter
- Baader Varilok adjustable T2 extension
- TS T2 to 2" adapter
- Quark attached from the 2" housing
- 0.5x reducer (Daystar)
- Tilt adapter (Rowan)
- ZWO ASI178MM

I'm also operating AVX and DIY focus motor, but they obviously have nothing to do with this issue.

I used SharpCap 2.9 for capturing. Due to the camera-optics combo I used bin3 option and 1 ms exposure times with gain at 60. This results into 30 fps and while being a bit slow for fast moving details, that ain't the problem here. I did stack with Autostakkert3! (best 10 % out of 2000 frames), processed the images with ImPPG and colored the images with Photoshop CC. Processing is identical for all the images.

By looking at the images you'll see that while adjusting the Quark and keeping everything else constant, dark areas start to creep in into the picture and the issues gets worse the more I turn the Quark's knob counter clockwise. This actually looks much worse than with the previous Quark. The results are pretty obvious and while flats will undoubtedly fix some of the issue, I don't think the image should look like this. At least it didn't with my previous Quark.

I really hope that I wouldn't need to start contacting Daystar again. Last time it took several months before I finally got them to replace the Quark (they told me that they had email issues and so on) and when it arrived, it was already -15 degC here in Finland and I couldn't test the unit until today. I've also had a lemon reducer from Daystar so one might understand my frustration with them. It takes forever to get in touch with them, then ship items back and forth and with such a short summer here at 60.2 N 24.8 E, this is not the optimum.

Any comments, suggestions of what to do and thoughts in general are highly appreciated.

Cheers,
Tommi

-5:
Image

-4:
Image

-3:
Image

-2:
Image

-1:
Image

0 i.e. knob pointing towards the camera
Image

+1:
Image

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cmas
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Re: Uneven image with a replacement Quark

Post by cmas » Sun May 07, 2017 4:38 pm

I also checked today the raw videos. Varying seeing, best at -5 ja -4, others so and so. Just a swift of thin clouds during -5 data acquisition for less than 5 sec and no clouds of any kind in other videos. So, to me, the uneven darkening of the image looks like something generated by the Quark.

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Re: Uneven image with a replacement Quark

Post by PDB » Sun May 07, 2017 4:46 pm

Tervetuola,

Looks indeed uneven. Looks like the dark area shifts from the right to the left when dial setting is rotated clockwise. From what I have been reading on the forum most of the Quarks will probably show this but it looks fairly "heavy". Have you checked that alignment in the scope before the Quark is correct (or the focuser is in alignment)?
(Noticed you use a ASI178MM and I am surprised seeing these images. If I use my 178MM with the Quark and focal reducer i get a hatched pattern all over the image.)

Regards,

Paul

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Re: Uneven image with a replacement Quark

Post by cmas » Mon May 08, 2017 3:05 pm

The scope produces very good images e.g. from the moon with just the OTA + IR-pass + ASI178MM and the OTA has been treated like "the most precious thing". So, based on the image quality alone I'd say there's nothing wrong with the optics. The focuser should also be AOK. Anyway, the only thing between the images is the Quark tuning so even if the focuser would droop a bit, it shouldn't affect the images like this, or should it?

Can you provide a link to those topics where you've seen others saying something about the "darkening"? Do you, or anyone else, have an idea why the Quark is doing this? Is it related to batch processing during manufacturing and "physically-not-so-even-as-with-the-more-expensive-etalons"?

I was thinking I need to do further testing in order to see what the image quality is with the other knob settings and with flats taken into account. I just compared these photos above to the images I acquired with my previous Quark and indeed there is some darkening also there but not as severe as here. Looks pretty weird to me.

One thing I also noticed, was that with this Quark I'm not able to see protuberances on the limb as easily as with the previous version. My avatar is a good example of a single video and no extra processing for the limb and that image was produced with that previous unit. Maybe this is linked into this new Quark (smaller FWHM than the old one?) or maybe the protus were just not as visible. There seems to be lot going on with this Quark that I'm currently operating.

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Re: Uneven image with a replacement Quark

Post by PDB » Mon May 08, 2017 4:34 pm

Hi,

here is one link viewtopic.php?f=4&t=21379&p=196628&hili ... en#p196628
If you do a searcht with the words "quark uneven", plenty of results.
Also read Alexandra's story: viewtopic.php?f=4&t=22079 (and Valery's remark)
If the new quark gives darker images then this is probably narrower bandwith. But think I need to leave this to be answered by the experts on this forum who have much more knowledge and experience on these topics than I have.

Rgrds,

Paul

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Re: Uneven image with a replacement Quark

Post by cmas » Mon May 08, 2017 5:42 pm

Thanks for the links. The overall image is not darker, just the proms were hard to catch. Oh boy what a situation...almost similar to Alexandra's.

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Re: Uneven image with a replacement Quark

Post by Valery » Mon May 15, 2017 1:39 pm

You need to work at -3 position. Looks like this is the best overall position.
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Re: Uneven image with a replacement Quark

Post by Astrograph » Thu Jun 08, 2017 4:31 pm

cmas,

The Quark is a budget filter that is subject to very little QC. That is why it is relatively cheap. A Chromosphere Quark should be 0.5A if used at F30. The narrowest bandpass of Quark we had was 0.14A according to Daystar. It also happened to be quite uniform which is very rare. Normally the more narrow the bandpass of a Quark, the more likely it is it will show non uniformity. Some Quarks can be very good, others very very bad. We used to check Quarks before supply and return if not good enough (which does not mean perfect). Daystar eventually said they would no longer exchange. We no longer deal with Daystar.

Your scope with the Quark is actually operating at F25.8 rather than F30. Therefore if it were a 0.5A Quark it will act more like a 0.7A. If your 80 is the early model it has a Crayford focuser which is likely to tilt. The later version has an R&P which won't. This will mean you need to adjust tuning to compensate for this.

Please see this link https://www.flickr.com/photos/alexandra ... ed-public/ to see a tuning test carried out by Alexandra Hart. This was a Quark supplied by us and of good uniformity and tight bandpass. This was running at F30 and the focuser was a 3.5" feathertouch. Therefore the non uniformity you see in these images is nothing to do with the scope, focuser or even the Quark. It was all down to tuning for the conditions on the day.

Having said this Alexandras Quark then went wrong and would not tune properly. Daystar failed to repair it once, then replaced it against our instructions with a POS. They have now refunded.

So to cut my waffle short. Your Quark does not look so bad at-3. It may be different to your earlier one but its by no means as bad as some. You should take a flat anyway to deal with any remaining banding.

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Re: Uneven image with a replacement Quark

Post by cmas » Thu Jun 08, 2017 5:41 pm

Yeah,
Thanks for the input. Highly appreciated!

This one, after some extensive testing, works quite OK after all. And I know the limitations of my OTA. I figured I'm just gonna stick with this unit. After all, when seeing allows, the results are not that bad. Some uneven parts in the photos and some "soft" areas even with flats, but I just usually crop them out. "-1" setting seems to give better surface detail than "-3" when seeing is same for both settings so I stick with "-1". The surface details are better than with my previous Quark but more uneven images come out. So, as you said, this might be with a bit narrower band pass, but at the same time a bit more uneven.

These animations suffer partly from Newtown rings as the flats recorded before and after 2h 13min session did not work for all videos. Something probably bends between the Quark and the camera although the system should be rigid. I have to look into this a bit more. The still image can be clicked for slightly larger version.

Image

Image

Image

Image

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Re: Uneven image with a replacement Quark

Post by Montana » Fri Jun 09, 2017 9:01 am

Wow! these are incredible images, I wish I had your Quark :)
Alexandra

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Re: Uneven image with a replacement Quark

Post by Astrograph » Fri Jun 09, 2017 10:27 am

Careful what you wish for Alexandra....

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Re: Uneven image with a replacement Quark

Post by Montana » Fri Jun 09, 2017 11:21 am

No I don't want another Quark! :lol:

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Re: Uneven image with a replacement Quark

Post by Astrograph » Fri Jun 09, 2017 11:32 am

I will put a Solar Spectrum on a chain and gently swing it back and forth in front of you next time we meet up....your eyelids are getting heavy.....you are seeing a nice yellow filter on your scope....you are smiling..... ;)

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Re: Uneven image with a replacement Quark

Post by Montana » Fri Jun 09, 2017 1:16 pm

All I have to do is think about my holiday when I used one on a TEC180 in Italy (with Luca Valentini), fantastic combo :) pity I have spent every last penny on this eclipse trip ;)

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