Search found 828 matches

by oopfan
Thu Aug 17, 2017 3:54 pm
Forum: Gallery
Topic: M27 with ASI120MC
Replies: 22
Views: 6748

Re: M27 with ASI120MC

I just received a reply from Sam at ZWO. He confirmed my suspicion that Gamma is applied in software, after digitization. He recommended always keeping Gamma at 50 for imaging. He did not comment on changing Brightness (i.e. Offset) to 10 (from the default of 0), so I guess that he sees no danger in...
by oopfan
Thu Aug 17, 2017 3:19 pm
Forum: Gallery
Topic: M27 with ASI120MC
Replies: 22
Views: 6748

Re: M27 with ASI120MC

Dave, I finally got a clear night. With regards to star detection using OpenCVStarDetector, the number of stars detected increases significantly when I boost Brightness from 0 to 10 and Gamma from 50 to 75. That seemed to be the best combination. That along with Gain of 100. Still, though, I cannot ...
by oopfan
Tue Aug 15, 2017 4:55 pm
Forum: Gallery
Topic: M27 with ASI120MC
Replies: 22
Views: 6748

Re: M27 with ASI120MC

Well, I looked at the datasheet for the AR0130CS from ON Semiconductor. The chip has a built-in A/D converter and 12 bits of digital output. There are inputs for gain for each channel but no mention of gamma. So it looks to me that gamma is being applied after digitization by either ZWO firmware on ...
by oopfan
Tue Aug 15, 2017 4:01 pm
Forum: Gallery
Topic: M27 with ASI120MC
Replies: 22
Views: 6748

Re: M27 with ASI120MC

Hi Dave, I joined the ZWO User Forum and posted a topic. Who knows if I will get a reply. Of the three inputs (Gain, Offset and Gamma) that I would like to tweak I am most curious about how ZWO implements Gamma "Correction". Here is my supplemental post that expands on Gamma. Dave, do you ...
by oopfan
Tue Aug 15, 2017 1:16 pm
Forum: Scripting
Topic: Helpful IronPython libraries
Replies: 19
Views: 3754

Re: Helpful IronPython libraries

No worries, Robin. I got some very helpful advice from Dave. With some luck the skies will be clear tonight. I am going to play around with the camera's brightness and gamma settings to try to get OpenCVStarDetector to see more stars.
by oopfan
Mon Aug 14, 2017 4:04 pm
Forum: Gallery
Topic: M27 with ASI120MC
Replies: 22
Views: 6748

Re: M27 with ASI120MC

Thanks, lots to learn. Recently I began using Gain of 25 (instead of 50) for DSO's with my ASI120MC and exposures of 120sec. I got the idea from this gentleman's photo of NGC 4565: http://astrob.in/290513/0/ If you click on the image and then click on the full resolution button and then pan over to ...
by oopfan
Mon Aug 14, 2017 3:30 pm
Forum: Gallery
Topic: M27 with ASI120MC
Replies: 22
Views: 6748

Re: M27 with ASI120MC

Thanks, Dave. For star detection it looks like I should play with Gamma too. I now see that adjusting brightness doesn't really do a histogram stretch -- instead it appears to just shift the histogram left and right (hence the term "offset"). Gamma, on the other hand, appears to have a str...
by oopfan
Mon Aug 14, 2017 1:26 pm
Forum: Gallery
Topic: M27 with ASI120MC
Replies: 22
Views: 6748

Re: M27 with ASI120MC

Hi Dave, This is very useful information, thank you! I have a question about the histogram. You said: "Camera setting Brightness adjusted to 10 to bring histogram away from left-hand side (ensures no data lost)" I have not played with this, ever. I must plead ignorance because I never knew...
by oopfan
Mon Aug 14, 2017 12:43 pm
Forum: Scripting
Topic: Helpful IronPython libraries
Replies: 19
Views: 3754

Re: Helpful IronPython libraries

Hi Robin, I think that you mentioned that the documentation of the "SharpCap.ImageProcessing" assembly is a work-in-progress. Do you know if there is anything in there that would allow me to stretch an image? Hopefully that will give OpenCVStarDetector more meat to sink its teeth into. Tha...