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

["Jack Swaton @ Starry Host" <jswaton@starryhost.com>]

Also,
If you want a Denk II Binoviewer (a fabulous item) you'll need a 2"
focusser.

Jack

-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
Jacob R Lauser
Sent: Sunday, October 08, 2006 1:38 PM
To: Marco
Cc: AMT LIST
Subject: Re: [ATM] 1.25in Versus 2inch focuser.


I'll be a bit less technical and say that 2" focusers are just "cooler".
Plus, 1.25 inch focusers on a 20" f5 will look puny. ;)

- JL

On Sun, 8 Oct 2006, Marco wrote:

> Which should I consider for the following scope:
>
> 20in F5 mirror. I ran SEC and consulted my local mirror supplier and 
> 83mm (3.27in) seems to be the best match in both Kriege/Berry's book 
> and in SEC.
>
> 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.
>
> My question is, what advantage would I get from fitting a 2in focuser 
> if the 1.25inch eyepiece gives me my maximum practical field of view.?
>
> For that matter, is there any point in fitting a 2in focuser to 
> anything F5 or faster?
>
> any illuminating ideas?!!
>
> Marco.
>
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>


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