Flat frames have vertical "divider" line in the middle

kamylko

Hi all, thank you for reading this.

From the last Asiair firmware update I started to have problems with taking flats.
I have Askar FRA500, ZWO EAF, ZWO Asiair Plus, ZWO ASI6200MC, Optolong L-Pro filter.

Let me briefly explain:
I use LED panel for a year now, always the same camera, always the same filters, same settings on the panel, basicaly every piece of hardware is the same. But for the last two session I started to have problems with taking flats.

First it was a horizontal lines, and I learned that it could be due to the exposure times, and also help in Asiair plus says that I should lower the brightness of light source to get shorter exposure.

My first concern is: everything worked fine and all of the sudden the same setup stopped working correctly.
So I partially solved the problem by using multiple sheets of white paper, but why?

The second thing after I solved the first one: A vertical line started to appear on all of my flats. It is at the same spot when I rotate the panel,when I rotate the camera or when I remove filter. It it there if I shoot via Preview mode or Autorun mode. So now I can not create a flat in any way, because the line is always there. It looks like a software issue to me. Is there a way to setup my current HW to work again the same way?

Thank you very much for your help !

PMTeam@ZWO

kamylko Hello, can you provide a few original images of the fits file? Thanks in advance

kamylko

I did also different light source and I took a picture of the sky in the morning. The same vertical line is there.
Here is google drive link: https://drive.google.com/drive/folders/10vf0x6-w_znyPJvbTf4icTRgRa0ov9zk?usp=share_link

Photo with stars in made in the morning, photo with weird lines is a flashlamp behind a few sheets of paper and the last one is the LED panel I normally use.

I thought maybe the filter is broken or something, but this vertical line is perfectly in the middle and it is not there on my light frames and dark frames. ONLY flats :/

w7ay

kamylko I thought maybe the filter is broken or something

It is probably a flaw in the camera when using short exposures.

What are you using as exposure times for the flat frames? Try to create the flat frames at exposures of greater than 1 second. If the light source is too bright, use more T-shirts, or better, neutral density sheets like these:

https://www.amazon.com/gp/product/B08GS1CLTJ/

Chen

maplearn

I had the same problem when I was using a second guide/finder camera. Fixed when I turned one camera off.

kamylko

I have learned that this is common due to the manufacturing process of full frame sensors and it will be calibrated out during the stacking process. Vertical line is there because full frame sensors are made in two halves and then put together. So this is the dividing line between the two halves. Also It is there when I am using my camera via PC with various software. And it is not dependent on the exposure time. I created multiple exposures up to 30 seconds, the line is still there.

So now I know what caused it, why it is there and it does not have any affect on the image.

Thank you all for your help.

kamylko

PMTeam@ZWO

Hi, they are still available here: https://drive.google.com/drive/folders/10vf0x6-w_znyPJvbTf4icTRgRa0ov9zk?usp=share_link
Also there is another discussion available here: https://www.cloudynights.com/topic/873309-flat-frames-have-vertical-divider-line-in-the-middle/

Thank you