Single wide vertical band in ASI6200 images

cwiecha

Folks -- I have been imaging with the 6200 OSC camera for a couple of years and often obtain images like those attached with a single wide band starting at the lower edge of the frame and extending upwards about 1/2 way.

I have attached two examples, one is after PIxinsight batch pre-processing with bias, dark, and flats applied but no post-processing other than background extraction and histogram stretching. The second image is stacked w/o flats (obviously :-) nor darks or bias in Deep Sky Stacker just to see if the band is an artifact of Pixinsight -- but it still appears. Note that I omitted dithering in these examples so perhaps that is contributing...I will reshoot next clear night but wanted to see if anyone has any ideas in the meantime...

The band is not super bright so I have marked it with the white oval in both images.

I did send some example images in to ZWO after originally getting it and seeing this but nothing unusual was found by their support.

Thanks for any suggestions! Charlie Wiecha

Kevin_A

cwiecha the circles in your photo besides the sensor stitch line look like frost, if not then that is a whole bunch of dust motes! Haha I would get frost if I did not cool gradually.

cwiecha

I've super stretched these to make the banding more visible but it's still noticeable even with normal processing so I'd love to get rid of it :-)

Tech@ZWO

cwiecha Need the raw images for analysis, could you share it with us? thank you.

Kevin_A

The 6200 sensor is made up of 2 sensor chips that are oriented and stitched together side by side. The line you are seeing could be that split. Sometimes it can be seen in raw data images but will be removed doing calibration frames. Stretch the image to the max and if it is perfectly in the center then that is it. It is fairly normal and not much you can do but remove it by calibration frames.

cwiecha

Kevin -- thanks for your reply and sample image. I suspect that's exactly what's going on. As requested, I'm linking the raw fits file here for the ZWO folks to look at:
https://drive.google.com/file/d/1IudNn2VdqIba64gvqa105E-6fksCmPFJ/view?usp=sharing

What's still a bit interesting is while the right edge of my "band" does seem exactly at the center I also seem to detect some actual width to the band, i.e. there is also a left edge some few 100 pixels away. At any rate I will assume all this is due to the split chip and try to calibrate it away with dithering, darks, bias, etc etc.

Charlie

Tech@ZWO

It does look exactly like kevin said, but if so, the line should can be calibrated via flat.
Did you please check your master flat and master light? can you see it on the image?

cwiecha

Yes, the 2nd image was the one without the flats...there is a bunch of dust I'm sure but the first image cleans up pretty well with the flats applied.

Thanks Kevin and ZWO Tech for clearing this up for me after wondering about it for a couple of years :-)

Charlie