comparing 2.1 hours vs 7.8 hours exp.time

hi folks,

cloudy nights - no new data - so I was playing around with old data.
here is a comparsion between an image of 7331 I have taken last year and this year.

the data is on the image.
except:
image acquireing software last year: SX oroginal - 2,4 and 6 min subs
i.a. software this year: astroart 4

to me it is quite astonishing, that there are only a little more stars in the background,...perhaps there are simply not more in this region...
on the other hand those almost 4times more data brought up star colors very nicely. (and also the galaxy)
difference in detail is mostly due to better seeing and transparency - and of yourse more single frames to reduce issues from the CCD.
well, one could expect that after 4times more exp.time there would also be more luminosity in the galaxy's periphery...but I think I would have to add much more time for this purpose...

here is the image with all data:
http://www.stargazer-observatory.com/7331-comp.htm

thanks for looking,

Dietmar
www.stargazer-observatory.com

Amazing shot Dietmar. Quite a difference in the detail due to a much larger exposure... specially in the galaxy core/dust lane area. Also the stars look much nicer due to an increase in the color...

Thanks for the hard work, and for sharing! 8)
Keep'em coming!

Interesting comparison, Diets! There could also be other factors at work: slightly different optics (AP reducer vs. TV reducer). Also, I see you used different cameras. I don't know if one is more sensitive than the other, but I wonder if that also came into play?

Either way, both images are very nice!

Eric

Both are excellent but the longer exposure has depth of color and better S/N.

Tom

Dietmar,
Yes indeed this is an interesting comparison. (Great images BTW).

I know that the reducer, camera were different as were the conditions and processing, but I wonder if total exposure time tells the whole story. I believe you are saying that there were 2,4,6 minute subs in each example. In the 7.8 hour example there are just more?. Are they in the same proportion?

I am interested because if they were the same times on subs, I would expect the same depth and just less noise with more subs. What would be interesting would be to keep the # of subs the same but increase the time with each of the subs. In this case I would expect more depth *and* less noise (unless light pollution would be a factor.

Richard, I would be interested in seeing any of your work ups on S/N particularly as it relates to # of subs, sub exposure time, camera read noise, and total exposure time.

Very interesting Diets. There isn't a lot of difference.

Greg.