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I am trying to problem solve an issue with possible overcorrection of amp glow after integration or perhaps some unwanted input from BPM. I had to retake my darks in a dark basement (Camera cooled to same temp) as my original darks were not done with proper gain and offset as those values had reset to zero in SGP without my knowing. And yes, the 20 darks were taken at the same duration (180 sec) and gain/offset 113/10. Camera is a Zwo AS183 OSC using the dual narrowband X-treme filter. I am also getting some banding. Light frames totaled 8.5 hours. I did get the "Warning" about a serious data issue regarding underexposed data, masterdark frames, light leakage although the retaken masterdark looks okay. I am inexperienced with APP and still learning. Hopefully, the jpg's will copy okay below.
Thanks, Lonnie
If you get that warning than there's something wrong when calibrating the lights, either your darks are substracting too much in the background or your lights are underexposed (resulting in the same thing). Looking at the screenshots I am wondering about the brightness of the darks overall, they do look a bit exposed by external light. Are you able to completely cover your scope? Or maybe even taking the camera off and cover that so you're sure no light can enter, darks don't have to be taken on the scope.
Hi Vincent, yes I see that my first attempt at redoing my darks may have been compromised. I redid them last night with extra attention to complete darkness around the scope/camera and will give it another go today. thanks. Lonnie
Well, I redid my Darks and Dark Flats (in the fridge to keep out light) with camera cooled to same temp as lights (-10 C), and of course matched to same exposure times as my lights, ran an integration for Ha-OIII extract HA and still looks quite bad. Not sure what I am messing up here. Can someone take a look at my data to find out what is going on? If so, what would I upload to your file station... original integrated image file, masters, and or original lights, darks, flats, and dark flats? Any help would be most appreciated. I really am a bit lost. The scale Master dark is unchecked and the adaptive pedestal reduce amp-glow is checked. I am using the Zwo AS183 OSC. Edit: I did notice that the gain of my lights were actually 113 and darks were made with a gain of 110. Would this create the problem shown on the integrated image?
@ldittrick Hi Lonnie,
ZWO recommend a higher offset for this camera at gain 130. That is not quite the gain you are using, but I'd still recommend to use at least a gain of 20 or perhaps even 25. See Appendix B at
ZWO produces the same binary drivers for all software, even if non-ZWO software in general do allow to set the offset manually.
Having said that, the bias should have EXACTLY the same settings as the darks and lights so, yes, the same offset. Not sure if that will fix the issue with the amp glow in this case because of the offset used.
Wouter
Thank you Wouter, I may just have to retake images with those recommended settings. Reading into the literature I am understanding more about Gain and offset. So with the darks in particular, a higher offset would shift the histogram to the right, preventing clipping of some information which would likely prevent a mismatch between the master dark and integrated light frames? Is there any way I can adjust my darks with different gain/offset values to salvage what I have to lessen the amp glow I have on my current set of lights? I would hate to lose two full nights of imaging, esp in the Cleveland area where cloudless nights are a challenge. If not, lesson learned. Thanks again for your help.
@ldittrick Hi Lonnie,
Shooting darks with a higher gain will not work with the lights you currently have. This will clip pixels in the lights. You may want to try with the same gain as the lights and see if that helps. Another question: did you use SGP for both the lights and the darks? If not, please do and see if that helps.
Wouter
