QHY268M gains & modes - Forums

Topic starter

Nov 19, 2021

Hi,
I just got my 268M with CFW3 and 36mm Baader filters. So, what gain do you use? According to the QHY website, you should start with mode #0 and gain 26, which I will do, if the clouds sometimes vanish… What is your experience? Anybody using modes #2 and #3?

Clear skies,
Chris

Stjepan Prugovečki

Nov 19, 2021

I got the camera recently, also still experimenting . Did few images with narrowband .
Used mode 1, gain 60 offset 45 with SHO filters and gain 0 , offset 40 with RGBs .
That was in Bortle 5 , with LED streetlights around. Two SHO images are here in my gallery .

Christian Schulbert

Topic starter

Nov 19, 2021

Stjepan Prugovečki:
I got the camera recently, also still experimenting . Did few images with narrowband .
Used mode 1, gain 60 offset 45 with SHO filters and gain 0 , offset 40 with RGBs .
That was in Bortle 5 , with LED streetlights around. Two SHO images are here in my gallery .

Hi Stjepan, nice results so far! Did you use any dark frames? It doesn't look like darks are needed any more with this sensor...

CS,
Chris

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Stjepan Prugovečki

Nov 19, 2021

I did use darks, however, more the habit than real need . Especially if you dither , stacking process takes good care of hot/cold pixels. As it was cloudy/rainy when I got the camera I just made a library , so I am using it on "does not harm , but does not help much either" principle.

. I have also color version of the same sensor and in fact stopped to use darks there.

rhedden

Nov 19, 2021

There was a discussion on Cloudy Nights last February about optimal settings for mode 1 (high gain mode). The consensus was that Gain 56 was a good choice. Qiu Hongyun from QHY stopped by and recommended it for short exposures. I have been using Gain 56 with offset of 10 since I got the camera, and the results are excellent.

https://www.cloudynights.com/topic/754530-qhy268m-read-out-modes-questions/

I also have Baader 36 mm filters, so your setup has some similarities to mine. The camera and filters are being used with a Sky-Watcher Esprit 100ED. One issue I have encountered is halos around brighter stars in RGB images, especially the blue stars. I need to remove halos with software every time I process an image. I cannot say for certain that the filters are responsible, but I think it is likely. The Baader H-alpha filter performs well, with minimal halos, and the red filter is also reasonably good. It's the green and blue filters that have halo problems with the optics I am using.

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Christian Schulbert

Topic starter

Nov 19, 2021

There was a discussion on Cloudy Nights last February about optimal settings for mode 1 (high gain mode). The consensus was that Gain 56 was a good choice. Qiu Hongyun from QHY stopped by and recommended it for short exposures. I have been using Gain 56 with offset of 10 since I got the camera, and the results are excellent.

https://www.cloudynights.com/topic/754530-qhy268m-read-out-modes-questions/

I also have Baader 36 mm filters, so your setup has some similarities to mine. The camera and filters are being used with a Sky-Watcher Esprit 100ED. One issue I have encountered is halos around brighter stars in RGB images, especially the blue stars. I need to remove halos with software every time I process an image. I cannot say for certain that the filters are responsible, but I think it is likely. The Baader H-alpha filter performs well, with minimal halos, and the red filter is also reasonably good. It's the green and blue filters that have halo problems with the optics I am using.

Thanks for your reply and for the link to CN.
Yes, according to the diagrams on the QHY-website, gain 56 for mode 1 and gain 26 for mode 0 are the optimum starting points. And gain 60, mode 1 is the best point regarding the dynamic range, as Stjepan uses.
Well, as usual, the only imaging, I can do with a new camera, is doing darks, biases and flats...
Do you use the new generation Baader "CMOS-optimised" filters? They should not have that strong halos at all!

Stjepan Prugovečki

Nov 19, 2021

My LRGB filters are Baader CMOS optimized, the latest generation and indeed some slight halo pops up on blue filter. I used it only on Esprit 120. Will try to compare with C8 Edge HD and with Esprit without focal reducer .
I have Antlia 3nm SHO and there are no severe halos on OIII . Halos are actually more visible on Ha , but nothing really worrying .

rhedden

Nov 19, 2021

My Baader filters are fairly old, so it seems likely that I will buy a new set in the spring to address the halos. I should have mentioned that they are not new filters in my original post.

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Christian Schulbert

Topic starter

Nov 19, 2021

Stjepan Prugovečki:
My LRGB filters are Baader CMOS optimized, the latest generation and indeed some slight halo pops up on blue filter. I used it only on Esprit 120. Will try to compare with C8 Edge HD and with Esprit without focal reducer .
I have Antlia 3nm SHO and there are no severe halos on OIII . Halos are actually more visible on Ha , but nothing really worrying .

Yep, regarding the prize of the CMOS-optimised filters against Antlia (and more so Astrodon and Chroma), it is obvious, that there must be some flaws :-)
I will see, how they perform in my setup.

Christian Schulbert

Topic starter

Nov 19, 2021

My Baader filters are fairly old, so it seems likely that I will buy a new set in the spring to address the halos. I should have mentioned that they are not new filters in my original post.

So, it looks like, the Antlia should be the most efficient solution. I think, there are some LRGB from Antlia available, too.

Stjepan Prugovečki

Nov 19, 2021

So far , from what I tried I am quite happy with both . Baader was a bit cheaper and available .
Can't exactly complaint on Baader as halos are not really worrying ,and also I am not sure that I have put the right sides towards the camera. It says somewhere that there should be small arrows marked on the filter edge to point to the right side, but I could not find it.
Long story short , I am happy with what I saw so far , with both Baader and Antlia

Michael & Jon Norman

Nov 19, 2021

We've been using high gain mode, gain 0 with lots of success. Looking at the published graphs, these settings seemed to offer the ideal blend between full well, read noise, and dynamic range. This works well for 5 minute broadband frames and 10 minute narrowband frames at F6.7. If you chose to use settings to reach a lower read noise at the expense of full well, I'd strongly reccomend dropping your exposures to no more than a minute to prevent saturating too many pixels.

Jon

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