I'm starting this thread to see if there are any owners of the the QSI 683 who have had the vertical banding issue and see if they have found a fix to the issue or found a method to calibrate out the bands. For those unfamiliar with the problem, the issue seems to be a very prevalent banding pattern that shows when frames are stretched very hard. Normally, you would expect to be able to calibrate out the bands through the use of bias, darks, and flats. However, for whatever reason, it seems that the banding does not always match up. For my case I've been able to subtract the bias from the darks and get what appears to be a band free master dark, but that is the extent of the luck that I've had. Using bias or dark frames on the lights or flats does not seem to work. It's been suggested recently that the cause may be taking images at low temperatures in the winter (<40-50*F) causes the fan and TEC cooler to run at only 30-40% and maybe changes the banding pattern. There seems to be some anecdotal and repeatable data that supports this, although not a full set of evidence yet. As a bit of a background, I've previously owned a QSI 683 and did not have the problem to this extent at all. I also own a QSI 690 and don't have the problem with that either.
What I hope this thread can generate is sort of a survey on whether a user has seen the banding, whether its been able to calibrate out with normal calibration and processing, or whether some other calibration method was used to produce desirable images. So if you are a QSI 683 user, I'd appreciate if you could take a couple of minutes to answer each of these questions and definitely would love to hear of any solutions.
1. Do you see banding in your stretched frames? (bias, flats, darks, lights)
2. Do these always calibrate out correctly with proper calibration frames?
3. If they don't always calibrate out, do you see a temperature dependency?
4. Have you found a solution to calibrate differently to remove the banding issue?
5. What have you tried if you haven't succeeded yet?
I should add that this has been discussed at length in the Yahoo Group here, https://groups.yahoo...18928?reverse=1 , and it has been determined by QSI that they were unable to reproduce the problem. They have a series of tests they recommend running, but as of now, it seems like assistance from that avenue is a dead end for now. They do suggest contacting them if you feel you can recreate the problem, so I have and am awaiting an answer.
All of these are obviously shown with an STF applied... The fits files can be found here... https://www.dropbox....IM3ZOzdx7a?dl=0
Edited by josh smith, 21 April 2015 - 08:41 PM.