How long do we expose for !!

[johnb]

Ive been imaging for a while now and whilst I appreciate you can never have enough data its all about how you capture it

For instance for M27 I took lots of 10 min exposures

Do I do the same for M13 and M45 - I guess not but guidlines would help - im sure everyone has thoughts and it depends on kit etc but are there any guides ?

John B

[roundycat]

Do a test exposure. Look for the longest time without star bloat or saturation.

Dennis

[ollypenrice]

...as above, but you might want to do some shorter subs if your DS target is a very faint. Without some shorts you risk burning out the star colour.

Olly

[johnb]

thanks I think i get the idea so for something really bright you take the long subs and some short

I found this on line for combining different exposures

Compositing 2 Different Exposures via Layer Masks

so i assume you can apply this process to any DSO's that have bright and dim areas like say M13 etc or even Andromeda ?

John B

[roundycat]

I have never found it necessary to use two exposures on a galaxy, or cluster come to that. M42 is the real exception because of its brightness range. The real secret is to get to grips with contrast stretching so you can do it without shifting the white point.

Dennis