"Robert Geake" wrote in message
...
"Chris Taylor" wrote in message
...

I noticed you had about 30 odd minutes of expsoure (74 x 30s) on your
image!
How come so many smaller ones instead of one bigger one? Again, i realise
that filters have their place and obviously in this case have improved
detail no end.

Ian Sharp covered this one pretty well. There are two additional reasons
that 30 seconds was used. The first being that light pollution here is so
extreme. Here's 30 seconds of uncombined, unenhanced exposure taken at
around midnight but with a wider field (interestingly M31 is just visible to
the top right of this image also):
http://homepage.ntlworld.com/taylor_...opix/NoLPR.jpg . Much more
than 30S would have far too much light pollution for a retrieval of the
galaxy.

Another reason is that the Canon 350D software allows programmable remote
control of the camera for a maximum of 30s. I now have a light pollution
filter and a programmable solution for longer exposures but alas, no camera.
Makes you laugh; doesn't it...

I have (somewhere at home) a 15 minute ISO 400 film
exposure(200mm FL) of M31 that i took on a crystal clear night(similar to
last night after rain that shows similar detail to your modified image.
I
will dig it out and scan it and publish a link to it over the weekend.

I'd love to see the picture. I've always admired the additional skill
requried to work with film and its apparent limitation compared with the
digital world. How would film have coped with the light pollution I'm
experiencing? Also, living so close to Heathrow, Gatwick and Farnborough any
extremely long exposures would leave a mass of unwanted intruders in any
widefield shot.

We have seemed to miss the main point of my post! The question i pose is
basicly how much proccesing is too much. The differences between your M31
pre and post proccessing are clear, at that point i would say thats far
enough, the image looks far better than the original and indeed, far
better
than any of us will see with our 1/60 eyes!

I got the point of your main post and agree; almost. There is so much more
that can be done to improve contrast etc. Some of which I'm still trying to
learn. Take a look at this guy's tutorial:
http://www.waid-observatory.com/article-psp-sharp.html for instance.

I agree that images can, and are often overdone but without the knowledge
and practice to begin with where to we get the experience from to determine
when the best has been achieved?

Looking forward to your M31.

Regards


Chris