Re: ATM secondaries shadow

[Stuart Field <field@lamar.Colostate.EDU>]

If you put a mask on the mirror of the same size as the secondary, it
will make no difference at all.  If it is bigger, then the resulting
diffraction will be as if your secondary were that size.  In other
words, as far as diffraction is concerned it does not matter where along
the tube the obstruction is - way out by the secondary or right against
the primary will give the same diffraction.

Stuart Field

Dwight Elvey wrote:

> The question is, would there be any advantage to
> putting a mask on the primary such that the
> secondaries shadow and close diffraction rings
> were masked? This would change the effective
> diffraction some but I'm not sure if it would
> get better or worse.