How long for M42?

[Black Knight]

Had my first imaging run last night using my ED80 as a guidescope. Much to my surprise, once I got the hang of PHD, I had no problems at all guiding, which was a bit of a result.

However, my images of M42 came out really quite rubbishtastic. The Trapezium area came out looking really quite bleached. I was using ISO800 with 2 minute exposures, so presumably that's too long. So what sort of exposure length should I be looking at for M42?

Oh, BTW, the camera is a modded Canon 500D.

[Bizibilder]

M42, as you have discovered, is not easy to image due to its dynamic range (fancy words that means it is made up from some very bright parts and some very dim ones!). So your 2min subs will be OK for parts of it. You will also need some subs at a shorter exposure to get the trapezium area correct - try 30 or 45 seconds. You then process each exposure length seperately. You can then "cut" and "match up" the bits of image you want using Photoshop or similar.

[Black Knight]

OK, that sounds good. When you say process them separately, do you mean when you stack them, or separately in Photoshop, prior to merging them? Or whatever. Come to think of it, that bit sounds really tricky, I'm not looking forward to that!

[Bizibilder]

Process all the subs for each exposure time seperately so you have several "finished" images each made of, say, 30 second subs & 2min subs. Then you combine the various parts of your final image from those. Hope that makes sense!

[Black Knight]

I think so . I'll give it a go anyway.

Thanks