Size of M31

[chiltonstar]

An imaging newbie's question:-

I have been playing about getting my set-up right using a DSLR (Nikon D300) with a 300mm prime lens, prior to attempting imaging using my ED80. However (see below) with M31 it is obvious that the FoV with the ED80 will be nowhere like big enough to fit the whole galaxy in with one series of images. Is the best strategy to use a focal reducer (quality compared with my 300mm lens?) or create a mosaic to get the full DSO in?

(image 6 x 30 sec exposures, f5.6, ISO2500, stacked in DSS; no darks or flats, tracking not yet perfect!)

Chris

[Beyond_Vision]

A 0.8x focal reducer/field flattener on the ED80 will just about squeeze it in and should produce better results.

[philj]

Yep it is big isnt it. A 0.8 reducer and compose the image so the galaxy lies diagonally across the frrame and you should fit most of it in.

Phil

[chiltonstar]

Many thanks for these comments; any suggestions for a focal reducer that will work well with the (Orion) ED80 and not break the bank?

I had only seen M31 with binos or small (up to 5") scopes, so I was a bit unprepared for how far the galaxy extends out along the longer axis (if I fiddle with the levels in the original image, it extends far further).

Chris