m82 with un modded dslr advice

[Ewan]

Evening all, finally got the cg-5gt to play ball after a factory reset, did the 2 star align then 3 calib stars then synced to Procyon & found i could easily do 90 sec subs, i wish i had used my finder illuminated ep before as im sure it has helped with the setup.

I see others have produced good M82' s with 20 subs of 40 secs @ iso 800 so am i overcooking it doing 90 sec subs @ iso 1250 ?

800 seemed to dim & 1600 too noisy but should i stay with 800 or maybe even mix 800's & 1250

Just need some advice as its a beauty of a night & the mount is tracking very well

Thanks for looking

[Jannis]

I wouldn't say 90sec is not too long. I'd go for 90 sec if you can do that with no startrails, and set the ISO so that the histogram roughly starts somewhere between 1/3 to 1/4 of the way from the left, and stay with that.

Stacking will take care of the noise anyway as long as you have high ISO noise reduction disabled on the camera and stack enough frames.

Personally i rearly worry about what ISO i use as long as i stay withing the maximim analog ISO of the sensor and the histogram looks OK.

In fact a higher ISO might give you more faint details even if it reduces your dynamic range and increase the random noise in each frame as you often increase the S/N ratio a bit.

I don't see how mixing ISOs would help though? Other then maybe by using a lower ISO with higher dynamic range for better star colors, but that's often easily recoverd in post processing anyway.

[Ewan]

Thank you Jannis ill stick with it then.