Re: [ATM] How far from the telescope should an artifical starbeplaced

["vladimir" <svla@isp.com>]

vladimir wrote:

> With the wavefront error at best focus (w) being half the
> surface error, the object distance in terms of the induced
> wavefront error is
> 
> (1/s)-(1/s^2)=w(R^3)/d^4

No good. I slipped up a bit. Instead of being halved, 
it should have been doubled, to:

(1/s)-(1/s^2)=4w(R^3)/d^4

which leads to
 
 s~[(d^4)/4wR^3]-1 

and object distance in units of mirror's f.l. resulting
in induced overcorrection error "w" is:
 
 s~D/512wF^3

This is not same as Suiter's formula, which is given for
the predetermined 1/4 wave overcorrection error. 

It probably makes it simpler to use the wavefront error
in units of the wavelength (1/4, 1/10 etc.) in which
case the above relation becomes:

s~3.5D/wF^3 for D in mm, or
s~89D/wF^3 for D in inches

Vlad



_______________________________________________
ATM mailing list http://www.atmlist.net/