M31

[Shibby]

M31 was actually my first ever DSO attempt (please don't look!) back in November, so now I'm revisiting it!

42x2min unguided, 26 darks. ISO 800.

I tried taking flats for the first time, but they only seemed to invert the vignetting, leaving me with red glows in the corners of the image. Not sure what I did wrong - were they too bright? Too dark? I took 26 of them.

PS: The image looks much noisier when compressed & uploaded

[SpookyKatt]

Looks nice, you've got alot of detail and the core isn't too

burn't out. I just took my first image of M31 last week and appreciate

that its a difficult target.

Kathleen

[Paxo]

Excellent image Lewis, plenty of detail in the dust lanes, outer regions and in the core, a nicely balanced image.

Steve..

[msinclairinork]

Well done! I would be happy with that!

thanks for sharing

michael

[Tom How]

That is a nice framing and a nice image. I like 206 sneaking in at the bottom. You are certainly heading in the right direction.

re the over-compensating flats, try taking shorter exposures for the flat frames so that the brightness of the flats is closer to that of the image frames - I've always wondered about non-linearity of DSLRs and flat frames.

Although from your commentry it is hard to tell if you took flats or darks or both?!?

[Shibby]

Thanks for the comments all and advice, I tried to keep it natural looking (which is hard with each monitor being totally different!). Yeah 26 flats and 26 darks have been applied tom. I took the flats by pointing the scope at a white laptop screen. Thanks for the tip, next time I will try darker flats. How do I find the 'average pixel value' in PS?

[Tom How]

You can probably just estimate it by loking at the histogram display on the camera's screen. The image frames will be all over on the left. The normal advice is to take a flat frame with the humps in the middle of the histogram - however if the camer ais non linear then you either need to correct hte flats for linearity or just take dimmer flats... of course, taking dimmer flats means taking more of then to reduce noise.

Astronomical ccd cameras go to a lot of effort to make sure there response is totally linear so that bright (ie low noise) flats can be taken and used to successfully calibrate dim image frames.

The best advise is to take a range of sets of flats at different exposures from a traditional halfway histrogram through to something with simliar brightness to your iamge frames and see which set gives the best calibration.

[SteveL]

If your flats are over correcting, you probably need to take bias/offset frames as well.

[Shibby]

Thanks for the tips, sorry for late response I've been at Oktoberfest (whoot!).

Hmm, according to deep sky stacker the bias frames are temperature-independent, so I could take them now and try stacking again?

[gary1968]

Nice one Lewis, its a big image mate and you have done it proud, better than my M31's to date.

Gary

[perrin6]

This photo makes me want to jump into my millennium falcon and head on out. Loverly ! Just got to make a packed lunch and off I go.

[Tim]

I like this one How does it look in a landscape view?

As Steve says, flats and bias frames work together.

[Shibby]

Here's a reprocess, I think I've dragged more detail out and the brighter image converts to jpeg much better:

Really makes me want a coma corrector though!

[Tim]

Its got a bit of a colour cast on my laptop screen this way, a bit cyanny.

[Earl]

Really nice image, my last M31 needs lots of work I have not had the clear skies without a moon to try yet.

The last image does have a tint if red but much better detail on the outer edges.

What did you use to take this image?

[Shibby]

Thankyou kindly for the comments & feedback; I do want to try and get it right.

What did you use to take this image?

Earl, it was just the equipment as listed in my sig.

Is this version any better?

It looks so different on each monitor!

[harry]

Lovely image. Could be my monitor but I prefer the colour of the first reprocess