Re: [ATM] Secondary Offset

[Mike Lockwood <melockwo@uiuc.edu>]

MItch,

Mitchell R wrote:
> I know this question comes up often but I want to understand the
> workings of Secondary mirror offset better. 
> Why exactly is it optically correct to offset it? 
> How much does it affect performance?

Not much for visual observing.

> Is it much more crucial on a larger mirror where it is usually a greater
> offset?
> Does a faster focal ratio need more or less offset usually? Is it more
> important in fast focal ratios?

Offset gets larger as the focal ratio decreases.

> How do you calculate offset?
> Is there a "rule of thumb" when it reaches a certain amount it is necessary
> to offset?

Maybe my secondary page will help - there is a section on offset:
   http://bi-staff.beckman.uiuc.edu/~melockwo/diagonals.html

	Mike Lockwood

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