From: "Dwight K. Elvey" 
To: atm{at}shore.net
Reply-To: "Dwight K. Elvey" 


Hi
 I don't know of an optical advantage of a SCT
that makes it that much better than a Newton for photography. The mount can
be more stable because of moment arms.
 Now, a Schmit camera is a different thing. You
place the corrector at the ROC of the primary ( Note: SCT it is at about
the focal length ). The primary is also over stopped at the corrector as
well ( the opening is smaller than the primary ). In this case, there is no
coma but the focal plane is curved.
 At least that is my understanding.
Dwight


>From: "Jack Schmidling" 
>
>Maybe I missed it, but I am really interested in an answer to this
>question......
>
>
>From: "John Sherman" 
>
>> Note that I said on-axis. The Newt is clearly poorer off-axis. If you're
>> looking for a photo-scope then the SCT is a great choise.....
>
>Could you please expand on that point?  I have been tryng to convince  a
>friend to dump his SCT's and use a Newt.
>
>Why is an SCT better for photo use?
>
>Bear in mind that the native focal length is far to long for most imaging
>and they are typically used with a focal reducer to get them down to Newt
>type focal ratios.
>
>js
>
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