Quote:
Originally Posted by Dazza81
Really, I've got a 15mm and 30mm so I'll give it a go with those ones tonight instead
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Dazza,
I suggest you start with the 30 mm, and get your target clearly identified and centred, before even thinking about using the 15 mm or 9 mm.
In your first post, you told us you have an 8" Dob - presumably with a focal length of about 1200 mm. A 30 mm Plossl would give you 40x magnification with a field of view of roughly 1.25 degrees.
With clear dark skies, the attached image (taken from "Turn Left at Orion"
http://www.cambridge.org/features/tu...2_and_M110.htm ) of the optimum view in a "Large Cat" would be a rough indication what you
might be able to see of M31 on a good night, but you also said you have light pollution to your North, so your view won't be as good or clear as this - the "Small Newt" image might be a better representation (but your field of view will be a bit smaller than the circle in this image. (By the way - "Turn Left at Orion" - the book
AND the companion website - are an excellent resource for a beginner astronomer!)
For your first efforts, you should probably concentrate on looking for galaxies and nebulae that are higher in the sky than Andromeda gets, and preferably in whichever directions have the darkest skies from your location. Once you have found a few, you will have a better idea of what you are looking for, and what they should look like at various magnifications.
