From: "Kreig McBride" 
To: 
Reply-To: "Kreig McBride" 


The really cool part about loooong focus telescopes is the high powers you
get with low power eyepieces, the flat fields and little or on coma.    Of
course refractors look cool also.  Oooops, guess were wern't talking about
refractors.  :-)

Kreig


----- Original Message -----
From: "Steve Houlihan" 
To: 
Sent: Saturday, July 12, 2003 9:36 AM Subject: ATM First Question (More)


>
> Thanks for all the replies.  One part of the answer is confusing.  Maybe I
> should have asked "What are the optical advantages of short focal length.
>
> Bill wrote
>
> >>The shorter focal length telescopes collects more light,
>
> This must be why they are called "fast" but doesn't make
sense to me.  A
> mirror of a given diameter and reflectivity should collect the same amount
> of light at any focal length.  Could someone please explain?
>
> By the way, I am not planning on making a mirror at this time, but will
> probably buy a 12.5 inch and build the rest.  At 12.5 inch and f/6 I can
> still stand on the ground and get the scope into my SUV.  At f/4 it would
be
> a lot more compact and closer to the ground.  I guess I am asking about
the
> optical advantages between f/4 and f/6.
>
> Steve Houlihan
> Santa Cruz, California
>
> sho{at}starband.net
> http://sho.mystarband.net/
> http://www.surfnetusa.com/sho
>
>
>
>
>

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