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Another clear night. Not bad for upstate New York. I seldom get this many clear evenings for a 6 hour shot.
Same as before with FLT 132, Baader filters SII, Ha, OIII 120 min each

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Comment by Robert C. Mills on September 19, 2012 at 10:02am

Thanks, I appreciate the input. I have a small spreadsheet that will calculate the minimum time for a sub-exposure based upon the average background value. It sometimes works. I shoot most of mine at 15 minutes.
I aslo have noticed some improvement in contrast by going to the Baader 7-8 Nm filters. I am also playing with PixInsight thatr seems to get "more" out of each frame.

Comment by Richard Crisp on September 19, 2012 at 8:08am

I can tell you that at 7 hours of data this image is nothign but grain when using emission line data

Comment by Richard Crisp on September 19, 2012 at 8:07am

I have lots of data to do that study... but here is how it works:

once you are calibrated so that the only noise sources are read noise and photon shot noise, you improve the SNR by a factor of two for every quadrupling of data you take....

it is very simple actually.

and a halving of focal ratio (ie, F/7 -> F/3.5) will collect data 4x faster giving a doubling of SNR for a given exposure time

Comment by Robert C. Mills on September 19, 2012 at 8:02am

There must be a cut off between 6 hours and 37.5 hours where more exposure does not improve the image that much more. That would be a nice study to do.

Comment by Robert C. Mills on September 19, 2012 at 7:58am

I flipped it inPS

Comment by Richard Crisp on September 19, 2012 at 7:35am

it is mirror imaged... but nice otherwise. did you use a newtonian or have a star diagonal in the image train? I am curious how it got mirror-imaged....

here's 37.5 hours of the same object:
http://www.narrowbandimaging.com/incoming/IC1795_ml3_ap155_L52_S34_...

Comment by Jeffrey P Nunnari on September 10, 2012 at 8:37am

Another work of art.

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