Andromeda Galaxy

14 years 6 months ago #24449 by michaeloconnell
Replied by michaeloconnell on topic Re: Andromeda Galaxy

The bigger the scope for a given F ratio the smaller the field of view.
Jed.

Agreed.

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14 years 6 months ago #24459 by markdj
Replied by markdj on topic Re: Andromeda Galaxy
Sorry for the confusion Eirik but there have been great images from 80mm scopes, aka Pete Lawrance.

I have seen m51 and it's satellite in 10x50 binoculars so anything is possible. Of course I did not see any detail, just a couple of smudges. As has been already said, a big aperture scope with a fast f/ratio of f/4 will allow you to see the spiral arms of m51. For galaxies, you need absolutely perfect conditions to see anything jaw dropping, star clusters on the other hand are more within your grasp.

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14 years 6 months ago #24536 by JohnMurphy
Replied by JohnMurphy on topic Re: Andromeda Galaxy
Sorry to keep the FOV story going.

Maximum FOV of a scope formula is:

(Field stop(mm) x 180/pi) / Focal length

The two variables here are field stop (either 1.25" or 2" usually) and the length.
This however is the maximum FOV possible. You really need to bring the eyepiece to bear.
True FOV at an eyepiece is:
apparent FOV of the eyepiece / magnification

magnification is calculated by:
Focal length of scope / focal length of eyepiece.

Therefore it should be apparent that the eyepiece is a tad more important here. The shorter the focal length of the eyepiece, the smaller the true FOV.

Clear Skies,
John Murphy
Irish Astronomical Society
Check out My Photos

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