First Galaxy's M81 & 82

[Mark-mck]

Here's my first attempt at imaging galaxy's (managed to pull myself away from the orion nebula for a while).

It's M81 & M82 taken with my 250 pds, Neq6 pro and Canon 1000d, unguided.

60 X 30s lights

30 X darks

i also managed to get 10 X 90s subs which i didn't use and was wondering how much more detail i'd get if next time i get the oportunity to shoot this pair i had a try at getting as many 90s subs as i can?

[JKB]

Very nice, thats my next target I think when skies are clear!

[rfdesigner]

I'd try taking some flats and reprocessing... there's quite a bit more data there.

I've had a quick try just removing the glow with the jpeg you posted, and it shows it's worth playing with.

Derek

[Mark-mck]

wow!!!! i took that?

how did you get rid of the glow?

[rfdesigner]

I use a processing program called IRIS, it has a 'subsky' command and fits a 2D polynomial in each of RGB to the image then removes that, I tried limiting it to a second order poly as I thought that would be sufficient, if you set it too aggressively you 'overfit' and you get substantial glow popping up in pockets where you don't want it.

I also logged the image to pull out the outer arms of M81, then reset the background after logging it and finally adjusted the RGB intensities as it was showing a touch green.

If you play with the origional data (which you should be able to build up to 16bit per colour or more depending on the program) then you will get a lot less noise.

Thanks for posting it, it looks like a good image.

Derek

[Bizibilder]

That's a nice image. You would improve things by getting more subs - better signal to noise for a start and you would stsrt to bring out some of the fainter details. With your scope and mount I reckon you could go to 2min subs without too many problems.

[Mark-mck]

Derek - i'm really impressed with what you've done with it, but unfortunatly what you said regarding how you did it went straight over my head. astronomy and photography are both new to me so i've still alot to learn, but i'll get there in the end.

Bizibilder - i managed some 90s subs with no trailing so i might try and push it a bit further next time i get it out, but i suppose alot will depend on how good my PA is? still getting to grips with that. and as for the ammount of subs i know i need to start concentrating on 1 or 2 targets a night but with it being new i get easily excited.

[rfdesigner]

Oh dear, I've done it again, sorry. Lets keep things simple

If you take 'flats' and divide the image by them then you will even out the cameras sensitivity across the frame, thus the glow will now be even at all pixels. Then you just offset the image.

Take a look at any online "how tos" about astro image processing and they'll hand hold you through flats. (the tutorial from IRIS for basic processing is: http://www.astrosurf.com/buil/iris/tutorial2/doc8_us.htm

That's 90% of the benefit, so get that working first then you can move onto curves etc.

Derek

[cloudbuster]

well done mark....thats a lot clearer and sharper than my first effort!