Re: ATM Colimnating a Newtonian with a perforated mirror?

["Tony Dunlap" <banjo2@bright.net>]

Take a piece of black paper, put the white spot on it, and tape it to the
back of the mirror so the spot is in the center of the perforation.


----- Original Message -----
From: Nick Martin <bonnyton@ednet.co.uk>
To: <atm@shore.net>
Sent: Tuesday, June 22, 1999 7:16 PM
Subject: ATM Colimnating a Newtonian with a perforated mirror?


>
> Dear list,
> The astronomical society to which I belong has been given access to a very
> nice 12" Newtonian. The only problem is that the mirror is perforated,
> presumably for use as a Cassegrain or similar. It is optically good but
the
> problem is how to colimnate it, other than doing a star test. A centre
spot
> is clearly impossible.
> Nick
> Nick Martin, Bonnyton House, By Ayr, Ayrshire KA6 7EW ,Scotland, UK.
>  Latitude 55 24'56" Longtitude 4 26' 00".
> "Eppur si muove" Galileo Galilei
>