Imaging M31

[abodee2]

Hi all,

We've got a clear sky forecast for tonight so I'm thinking about setting up at a local dark site tonight. I've just been observing since getting my scope but I'd like to try my hand at imaging tonight, specifically M31.

Now i've read a lot about darks, bias and lights on here and using them in DSS or Nebulosity 4 (to be honest i'm still absolutely clueless)  - Lights are the only real exposures of what i'm photographing and the other shots give the software i'm using information about the sensor/lighting/noise of the camera. The thing is i'm not really sure i totally understand how to take darks, bias or flats with my DSLR? 

Hopefully someone can give my pointers about how many light shots i should take of M31 and how many darks, etc. I was thinking of setting the exposure time ~30s @ ISO 800 for each shot - I'm also using a Canon 50D (un-modded) if that helps.

Any advice would be greatly appreciated!

Ali

[piprees]

You should have no problem with Andromeda. It's so big and bright you'll probably get a good result from say 10 x 30secs exposures or 20 x 15 secs. It's not really too necessary to take hours of exposures for this subject. See the tutorial from Forrest Tanaka on youtube, astrophotography without guiding, it's pretty inspiring. He takes loads of short exposures, totalling about 5 minutes!!!

Best of luck,

Phil

[gooselk]

Hi Ali,

Hopefully someone can give my pointers about how many light shots i should take of M31 and how many darks, etc. I was thinking of setting the exposure time ~30s @ ISO 800 

although it might be too late here's what I think:

As for the light frames I'd say you'll be ok with ISO800 and 20x30secs. If you want the fainter outer regions of M31 you can do another 20x60secs and later combine the different exposures to get the spiral arms without blowing out the core. That makes a total of 30 minutes of exposure which is not too much effort in time.

After having done that you should cover the scope and take 20x30secs and 20x60secs of dark frames. After that you leave the scope covered and take 20x1/4000th secs (or the fastest your camera can do) at the same ISO. Here're your bias frames.

Having not used flat frames for myself I can't really help you out there. I could just try to explain theoretically what to do as I know what they are used for but never made some for myself Others might be of more help here...

Clear skies ... Lars

[Astrosurf]

Good luck! The spiral arms of Andomeda are very faint so I've only got good detail by auto-guiding and doing 5 min+ subs. But do try 60s as Lars suggests. 

See here for DSOs:

http://dso-browser.com/

And here for how they'd look (Not NGCs) with your kit:

http://www.12dstring.me.uk/fov.htm

Alexxx

Alexxx

[PeterCPC]

For flats you want to take them without moving the scope from the lights position. I used to use a laptop but now use a tattoo LED pad with some grey acrylic on . Set the camera to AV, hold the screen in front of the scope and fire the shutter on the camera as many times as you need.

Peter

[gooselk]

See here for DSOs:

http://dso-browser.com/

Thanks Alex for this great site. A good source to plan your imaging for a specific night.

Clear skies ... Lars