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Here is an animation of 22x600s exposures autostretched with PixInsight. There is a large number of hot/warm pixels. Thanks to dithering, this doesn't matter when integrating frames, but when single frames are important, like for asteroid search and astrometry, the sheer amount of them are annoying. ThirdAsteroid.mp4 Is this a normal amount/density of warm pixels? Edit: Ah, I forgot, I used the wrong calibration frames (180s darks, should have used 600s) |
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| What offset did you use? And mode/gain settings? Are you using the latest all-in-one beta software pack? |
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Hi, I use from a 2 min to 10 min exposures depending on the object, and I do have lots of both cold and hot pixels using this camera, If you are using Pixinsight to calibrated, my workflow consist of prior using WBPP is to analyse each frame using Blink, follow by cosmetic correction, in CC I select an frame and tick both Hot and Cold sigma, I then use the Real Time Preview 'show map' and find the best Hot and Cold sigma number. hope this helps, Charles |
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Have you shot darks for the camera at the settings you used to take the subs? Peter |
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| This is a CMOS camera, looks more like a CCD camera. Are you cooling the chip?, if not, I would, it should help. |
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Here is an animation of 22x600s exposures autostretched with PixInsight. There is a large number of hot/warm pixels. Thanks to dithering, this doesn't matter when integrating frames, but when single frames are important, like for asteroid search and astrometry, the sheer amount of them are annoying. Dark current can vary between sensors but this is similar to what I see from my IMX455 based QHY600M camera. I’ve noticed that a lot of folks appear to believe that CMOS cameras don’t have dark noise, but that’s not correct. Remember that CMOS is still reading the signal from each pixel, which always contains some amount of dark signal. The main reason that CMOS cameras appear to have less dark noise than CCD cameras is because the pixels are generally smaller. Remember that the dark signal is proportional to the area of the pixel so cameras with smaller pixels will appear to have less dark current. You can indeed use the stacking filter to remove warm pixels but that’s not the same as subtracting the dark signal itself. Subtracting the dark signal does increase the dark noise, but that is a pretty small effect over the integrated stack if you build your master dark file from ~16 subs and you have 20-50 subs in your stack. Combining subtracting darks with dithering adds a spatial averaging component to further reducing the residual dark noise to a VERY low level. By simply using the stacking filter to remove the warm pixels, you still have spatial averaging, but you haven’t removed the dark signal itself. John |
