Re: [ATM] 1.25in Versus 2inch focuser.

["Mel Bartels" <mbartels@bbastrodesigns.com>]

> However in Berry's book it is recommended that in a scope of this
> size, parameters give a practical limt of around 0.5 degrees FOV.
> 
> Doing some calculation tells me that I only need a 1.25in focuser
> as a 24mm panoptic will supply me with a field of around 39 arcmin
> which is more than ample.


This is a mis-interpretation of the book.

A 20 inch f/5 (of which I have) yields a 57 arc minute FOV using a Nagler
31mm.  A real FOV of 1.7 inches is required.

For more, see http://www.bbastrodesigns.com/rft.html 

Mel Bartels


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