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Need Help with Vertical Stripe in Recent Datasets

Sky-Watcher EQ6-R Pro iOptron SkyGuider Pro Banding Troubleshooting
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Alex avatar
Alex avatar
Hello,

I picked up astrophotography two months ago.  I have been using my D780 with camera lens and a SkyGuider Pro for a while with no issues.  I just got my mount a couple weeks ago.  I have had three clear nights using my EQ6-R, William Optics GT81-IV, and Nikon D780.  The data from the first night seemed okay, but I did not take flats.  The data from nights 2 and 3 have a wide vertical stripe/band going through the middle of the image.  I didn't notice it much, but when I took flats the stripe became even more noticeable, but the issue was there without the flats.  I went back and added flats to my first night of data, and it seemed to get a vertical band to it as well, but the other issues that flats resolve were fixed.  I also tried stretching the heck out of the flats, but I did not see anything in the flats.

The vertical band starts out red at the bottom of the image and flips to green in the top half.  Looking at the optical train on everything with a flashlight, I didn't notice anything.  The first night of data was 2 minute exposures.  The 2nd and 3rd night were 30 second and 90 second exposures.  DSS and Photoshop for everything.

I'm at a loss for what to check next.  Here's a fully saturated picture to show what I'm talking about.  The stripe is also noticeable in my M42 image I posted to Astrobin.

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Aaron Hakala avatar
Aaron Hakala avatar
Not sure, but maybe it’s condensation? Either dew on the objective, or camera sensor. Are you in your back yard? Are you letting scope and camera acclimate?  Are you using dew heater? Just a thought.
Alex avatar
Alex avatar
Aaron Hakala:
Not sure, but maybe it’s condensation? Either dew on the objective, or camera sensor. Are you in your back yard? Are you letting scope and camera acclimate?  Are you using dew heater? Just a thought.

Yes, it's all been in my backyard.  I have not seen dew on the objective or anything else that I could see checking with a flashlight, but I am not using a dew heater.

I haven't necessarily been letting the scope acclimate, but usually it's only been a few degrees different between inside and outside, and I am still pretty slow setting up - 30 minutes or so.  That said, the days where the stripe shows up were during the really cold weather last week in the southern US.  First light with the EQ6-R definitely took a lot longer as I had to crack open the manual a couple times to remember how to use it.  Maybe that's a contributing factor.  I'll try not to stress out until I can get some more data.
John Hayes avatar
John Hayes avatar
It's hard to say exactly what might be causing that particular problem, but it's important to recognize that no sensor is perfect.  So many Canon sensors used to display horizontal banding issues that years ago someone wrote a "CanonDebanding" script in Pixinsight.  Clearly the sensor in your camera has a flaw that may be mostly minor for normal photography but becomes pretty obvious when you use the camera for AP.  The root of the problem may lie in variation in responsivity of the pixels along in those columns caused by a processing "glitch" when the sensor die was made.  As a first try,  I would personally try the CanonDebandding script in PI to fix it in the raw data.  I'm not aware of any other similar filters but there may be some out there.

In principle, flat calibration should get rid of this sort of problem but it can be tricky with an OSC camera.  Variations in color after flat calibration along the band is the most common side effect.  That's usually due to small differences between the spectral content of your flat panel and the sky.

My recommendation is to be very careful to make high quality flats to see how well you can remove this artifact through calibration.  You may wind up with small color artifacts, but in general, I think that you should be able to achieve a huge improvement over what you've shown here.

John
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Alex avatar
Alex avatar
Thanks John.  I haven't seen the issue in any images with my camera until the past two nights of use, which is my concern.  The camera is new and has really only been used for AP the past 2 months, so I am comparing it to nothing but astrophotos.  I've been trying some different flats to see if I can get it to help.  I'll have to try to learn PI at some point.  I do have Astronomy Action Tools in PS that has a vertical band reduction, but that band is ~240 pixels wide.

I'll keep trying.  Thanks.
Alex avatar
Alex avatar
Aaron, John,

Thanks again.  I think it was a combination of bad flats and over processing images.  I felt like I had started getting worse, not better, after getting new gear, and I was pretty bummed at the time.  I wasn't actually close to it, but I was thinking maybe I should sell my gear and get a new hobby even though I just started.

I am happy to say between taking better calibration frames and getting better at processing, I am super excited for the hobby once again.  Now I am contemplating a longer focal length scope.  I could really use something around 900-1000mm to match the pixel size in my camera.

Thanks again!
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