2022-08-17: APP 2.0.0-beta3 has been released !
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Strange Integration Result
I'm getting a very strange result from recent integrations. The image is very green and crosses appear on the image. Camera settings have not changed and I'm using darks and bias frames from my library that I have been using for months. I take flats after every session, and they appear to be calibrating fine. As a test, I used lights taken of the Eagle Nebula a month ago, used darks and bias from my library, and used flats taken recently from a session imaging Sadr. That integration results in an image that looks fine. Again, as a test, I used lights from a recent session imaging Sadr, Flats taken after a session imaging the Eagle Nebula a month ago, and darks and bias from my library. That image turns out to look like the attached image. It appears that the lights are the issue. I look at the individual subs, and they look fine. I don't believe the software is to blame, because I have re-done images with the corresponding lights/flats from a month ago (and even last December) and darks/bias from my library, and those images turn out great. I have uploaded some lights and flats from a recent session in the hopes that someone notices something that I don't. I'm using an ES 102 ED, ZWO ASI 294mc, with Optolong L Extreme. Looking for some help with this one.
Thanks in advance
@mfranks_160 Hi Mike, the red and blue wobbly lines are caused by hot pixels that walk across the image due to dithering or tracking imperfections. how often do you use the camera? It seems unlikely that there suddenly are much more hot pixels than before. You wrote that the camera settings haven't changed so can you please confirm that the darks and bias have been shot at -5ºC as well? Unfortunately APP doesn't store that info in the FITS headers of the masters.
I'll have a look at your data now.
@mfranks_160 Hi Michael,
It looks like the flats haven't been taken correctly. When I look at a light, I see the following image plus histogram:
The histogram shows that all three color channels have their peaks well detached from the left. Red and blue have their peaks more or less at the same place and green further to the right. The image looks green but that's expected because of the double amount of green pixels w.r.t. red and blue in an OSC camera.
The flats however look like this
The red channel is not detached from the left at all. Blue is and green is nicely to the right. This means that in the flats red is underexposed.
What light source do you use for the flats? Have you been using this always? How do previous flats look? do they have similar histograms as these flats or do they have the red peak detached from the left?
I tried integrating your data using the MD and MB you provided and got a warning that image calibration couldn't be performed correctly and that many pixels clip to black. Did you get that warning too? It suggests that your lights have a problem and are underexposed, which seems odd given the 300 sec of exposure time. Did you use any filter like L-eXtreme? There is no filter data in the FITS header.
@wvreeven Thanks for looking into this! I'm taking flats as I have always done. I put a white cloth around the telescope and aim for blue sky, making sure direct sunlight isn't hitting the front of the scope and using a setting of 17000 ADU. I use the camera whenever I possibly can, it's been a lot here lately due to clear skies. I'm using the L extreme. My guiding has been good with PHD giving me an error of around or just under 1. I look at the histogram for the flats on the FITS viewer and it seems that all channels are lining up. I don't understand why it says my lights are underexposed as I'm at 200 gain with an exposure of 300 sec, but I never got that warning. In your first response to me, you mentioned hot pixels. Like I said before, I have been using the camera a lot. I live in Texas, and we are currently experiencing higher temperature than normal during the day (Over 100). I leave my all my gear outside (it's been two weeks), making sure I cover both my imaging camera and guiding camera with a white t-shirt to protect them from the sun. Could I be "frying" camera with the heat? Could the heat be causing hot pixels to develop, making my dark library obsolete?
Could I be "frying" camera with the heat? Could the heat be causing hot pixels to develop, making my dark library obsolete?
It certainly is a possibility. Perhaps you can try to take new darks and bias and see if that solves the issues of the hot pixels.
I use the camera whenever I possibly can, it's been a lot here lately due to clear skies. I'm using the L extreme.
Did you use the L-eXtreme filter for your previous images as well?
@wvreeven yes I used the l extreme for the previous images also. I started taking new calibration frames today. We'll see what happens!
@wvreeven well I THINK I figured it out. I reinstalled the camera drivers and everything seems to be working now. I also believe I have a light leak in my train, but I can get that sorted out. Thanks for looking into this.