Originally posted by SunValley: Nicely done!
Why the shorter subs? Was the tracking sometimes off with the longer ones?
On nebulas and dim structures I tried to maximize the exposure time to get as many photons as useful into the single frames. In the beginning of this year wind conditions with a mount that is at its maximum load forced me to reduce the exposure time and rise ISO not to loose to much percentage of good subs (I never had imaged with ISO 1600 before). It worked quite fine. Starting on galaxies this year I remembered some testing I had made 2 years ago when I compared the effects of fewer but longer subs on lower ISO compared with more and shorter subs with higher ISO (this was the "gummybear test" thread here in the forum in Winter 2015/2016). That time it came out that - for me - it was better to use (less) longer subs for better dim nebulas but with more noise in the end and (more) shorter subs for galaxies with less noise in the final image.
It seems to me that enough shorter subs on moderately high ISO deliver better detail in the galaxies. And you have less loss due to wind gusts, mount effects etc. The stars do also look better than if I went for max. possible exposure. And if I leave the exposure relatively low I gain headroom for the bright stars not to oversaturate. I could also do hdr mixing techs to get rid of blown out stars but only on the cost of having less subs with the best settings for the DSO itself (and I am penurious with my light subs
).
Originally posted by gbeaton: Thanks Pete. Yes, your histograms tend to be to the left. thats what I was wondering. I guess with enough subs, this is alright.
I feel more comfortable on the left side of the histogram for some reason. But this is all relative because the position background peak is mainly depending on the skyfog brightness of the location. I try to get the target bright enough and the stars below 255/255/255. When the nebulas come back I certailŽnly will experiment again with longer exposures. My aim is to get into the region ob maybe 10 minute subs at very low ISO (e. g. for HA-images). But I already learned that this long time is risky because you easily loose valuable subs due to the mechanic conditions.