A place to post guides, instructions and HOWTO documents on the use of SharpCap and Astrophotography in general
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SharpCap normally deals with the image scaling if necessary - for instance it can usually find out the max pixel value from the camera SDK or ASCOM driver and then bitshifts the data to use the full 16 bit range. This is actually done mainly to avoid an enormous number of people asking 'why is my image so dark'
Hi,
I have a question about optimal exposure length. I have SharpCap pro. I have done the sensor analysis and have watched the YouTube lecture about optimal exposure length, gain, etc. I understand that with darker skies the calculated exposure times can be quite lengthy. I ran the exposure calculator plugin in NINA and linked to the SharpCap sensor analysis results. I'm in Bortle 2 (maybe Bortle 1.5) skies so I'm lucky. So the results that I obtain for my system after measuring sky background are:
Lum 841 s
R 2,103 s
G 2,403 s
B 3,364 s
NB 3 nm
Ha 16,823 s
OIII 16,823 s
SII infinity.
What would be some practical subexposure lengths for the various filters. I have been using 300 s or 600 sec subexposures. No issues with tracking or guiding. Plenty of satellites these days with Starlink though.
wow - nice dark skies! Given those figures the only thing to do is to take the longest exposures that your mount will reliably cope with. What model camera are you using? If it has high read noise then there may be a benefit to looking at models that have lower read noise (ie going from a CCD with read noise 8e to a CMOS camera with read noise 1.5e would reduce the calculated exposure times by a factor of ~28)
If you run in either of the 'extended fullwell' modes then the read noise is up in the 5.5e to 7.5e range and doesn't drop much with increased gain. However in the 'High Gain' mode, gain 56 gets a read noise of 1.6e, which may give you significantly reduced recommended exposure times and be more appropriate for the narrowband filters.
