+RonC Posted June 11, 2021 Share Posted June 11, 2021 (edited) Well I'm still learning after 10 years! Read an article about long exposures with a 183c CMos camera and the emphasis was on the Dark frames taken. So last night (in a brief clear sky!) I did some 300s Darks with everything covered then tried 10 x 300s exposures at Unity gain and 24 Offset on M13. Also got 2 x 300s on M27 before the clouds rolled in! I processed them this morning and was surprised at the result for a fan cooled cam! No sensor glow at all and the Darks x 10 worked really well. What I did notice is that I need to do some more longer exposure Flats and Dark Flats as there is a bit of vignetting. I will try to do them before Saturday nights forecast clear sky's! Comments welcome please.. Edited June 11, 2021 by RonC Link to comment Share on other sites More sharing options...
8472 Posted June 11, 2021 Share Posted June 11, 2021 Ron, were you shooting without darks prior to this? Link to comment Share on other sites More sharing options...
+RonC Posted June 11, 2021 Author Share Posted June 11, 2021 No, but using 90 - 120s exposures and I got the Flats just right for those! Link to comment Share on other sites More sharing options...
8472 Posted June 11, 2021 Share Posted June 11, 2021 Like my 294, the 183 definitely needs matching darks to ameliorate the starburst amp glow. Dark scaling/no darks doesn't work for these sensors. Link to comment Share on other sites More sharing options...
+RonC Posted June 11, 2021 Author Share Posted June 11, 2021 ameliorate, that's a new word for me! 😄 8472 1 Link to comment Share on other sites More sharing options...
+Graham Posted June 11, 2021 Share Posted June 11, 2021 It is a never ending learning curve Ron, That is what makes this hobby so fascinating +RonC 1 Link to comment Share on other sites More sharing options...
+RonC Posted June 11, 2021 Author Share Posted June 11, 2021 If the vignetting is dark around the edges, does that mean the Flats need to be a longer exposure or a shorter exposure? I'm getting stuck with this!! Link to comment Share on other sites More sharing options...
8472 Posted June 11, 2021 Share Posted June 11, 2021 24 minutes ago, RonC said: If the vignetting is dark around the edges, does that mean the Flats need to be a longer exposure or a shorter exposure? I'm getting stuck with this!! What acquisition software are you using? Generally, I tend to go for about ⅓ total sensor saturation (so about 20500 ADU) in APT. I am not familiar with any other software, but I'd be surprised if the same numbers don't still apply. It's so much easier with DSLRs! Link to comment Share on other sites More sharing options...
+RonC Posted June 11, 2021 Author Share Posted June 11, 2021 Using APT, ADU is 2089 Kev. Link to comment Share on other sites More sharing options...
8472 Posted June 11, 2021 Share Posted June 11, 2021 Ah, there's your problem then. That's far too low. Try using the CCD Flats Aid to take the guesswork out of it. Leave the settings at default, but I personally like to shoot a minimum 30 flats. Up to you, really. Link to comment Share on other sites More sharing options...
+RonC Posted June 11, 2021 Author Share Posted June 11, 2021 I think I just discovered that Kev, also the Gain was only 100 !! Link to comment Share on other sites More sharing options...
+Ibbo Posted June 11, 2021 Share Posted June 11, 2021 Depends on the bit depth. IIRC Ron is running at 8 bit ( and binning?) so max ADU is about 4000 and a 1/3 to 1/2 of that is what to aim at. Not sure about gain as when I do flats for my solar you can up the gain to get a decent flat. After 16 flats I think they say satistically there is little difference , saying that I do 31 as they don't take that long to do. Darks should match your imaging run settings as near as you can with cams with no set point cooling. Link to comment Share on other sites More sharing options...
8472 Posted June 11, 2021 Share Posted June 11, 2021 I've gone back and forth with the creator of APT previously on this very subject and sorry to say, I don't recall what the definitive answer was. I'll see if I can dig it out. What I do recall, in my camera's extended pixel mode (what I shoot with most), it drops from 14 to 12 bits. In the early days i shot my flats with the assumption the ideal ADU values were similar to what you were using and as a result, I also had terrible vignetting. In this mode, the 294 has vaguely similar characteristics to the 183, albeit in a larger sensor. Yes, you are right about the bit depth of the camera's ADC, but if APT is measuring from the output FITS file, i.e. post-ADC, aren't these by definition 16bit (0-65536)? I'm by no means an expert at this, so I'm genuinely curious. Kev Link to comment Share on other sites More sharing options...
+Ibbo Posted June 11, 2021 Share Posted June 11, 2021 We sorted this out about a month ago, well just about as I suspect there is still a slight light light leak or un equal illumination but it was minimal. The higher ADU flats were overcorecting Rons images. Link to comment Share on other sites More sharing options...
+RonC Posted June 12, 2021 Author Share Posted June 12, 2021 This happened because I tried using 300s at 1x1 Binning, I got the darks sorted but had to re-do the Flats to match. The resulting images were no better (in my opinion) than those I take at 120 - 180s but the 1x1 looks to have more definition. The ongoing saga continues..... Thanks both for your valuable input.. Ron Link to comment Share on other sites More sharing options...
+Ibbo Posted June 12, 2021 Share Posted June 12, 2021 (edited) So 1x1 binning could be running at 16 bit or 12 bit if 16 bit you want to aim for 21000/ 30000 ish as Kev states if 12 bit 1400 to 2000 which I think you have been running at (I was wrong when I said 8 bit) Edited June 12, 2021 by Ibbo Link to comment Share on other sites More sharing options...
+RonC Posted June 12, 2021 Author Share Posted June 12, 2021 Running at 12 bit Steve and using 2089 ADU Steve.. Link to comment Share on other sites More sharing options...
+Ibbo Posted June 12, 2021 Share Posted June 12, 2021 If it was me I would drop it to 1700 at least. +RonC 1 Link to comment Share on other sites More sharing options...
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