Andromeda Galxy - M31

Looks very good for the seeing conditions you describe.

ISO 1600 at 3mins is going to add a fair bit of noise and will reduce detail. I would try F2 to F2.8 at ISO 400 for 3 to 5 mins and see how that looks. If your tracking is fairly good keep the ISO down and put the time up.

I don't have a motorised scope so the above is just theory on my part but your 85mm lens is very good wide open. Usually when a lens is open it tends to degrade away from the center but given that the 300D has a 1.6 crop you won't encounter that the way a full frame camera would.

Lovely stuff Keith, great image. How could you improve it? Well I think Dave L hit it on the head, more exposure time would bring out better dust lane detail.

Keith one other significant opportunity for improvement would be to take multiple images and stack them to improve the S/N ratio. Also dark frame subtraction and bias calibration would help a lot too. If you could incorporate the above I think you would end up with an image which, instead of being fantastic, would be utterly mind blowing!

BTW I was out imaging M31 last night too. I hope to process the data set this evening. I'm hopeful for a decent enough image.

You were disappointed with the result of that photograph. I'm a late arrival to ameteur astronomy and can only dream of a result like that. I can't even level and align the scope yet. Still, that image gives me great hope for back yard astronomy

the only way you could improve on that is get more dust detail in the spiral arms. Smile

I'll try for that next time This is what i'll do.....

one other significant opportunity for improvement would be to take multiple images and stack them to improve the S/N ratio. Also dark frame subtraction and bias calibration would help a lot too

This is a stack of 8 eight shots, at different times and minutes exposure. I'll keep that IS0 down so, tracking is quite good, and take many multiple shots....

This has no 'dark frame', I must do this next, but don't know how to do it :oops:

Bias calibration : Wots dat???

Keith..

Must say, the standard of shots from everyone on this site really is top class.

Hi Keith,

Nice shot.

A dark frame has to be taken at around the same time as the light frame is. You just cover the lens / scope and shoot the same length as the light frame. Dark current is very temperature sensitive.

It is a good idea to take several dark frames to average together before using them to "calibrate" the light frames.

Dark frames reduce the "dark current" which all CMOS and CCD imaging systems generate over time. This is effectively a false signal.

BIAS frames measure the electronic noise introduced as the chip reads out the data. This is quite small, but you may as well remove all unwanted data!

To generate a master BIAS, take 20 shots with the camera covered at the fastest possible shutter speed. Then combine the 20 images to get you master BIAS.

The calibration process is usually done in software and you just tell your package which dark and BIAS to use and it does the rest for you.

Later,

Jed.