RE: ATM A few questions before I screw my Dob together for the first time..

["Rovelstad, Peder" <Peder.Rovelstad@standardregister.com>]

Thanks for the tip!  This begs another question...  Where can I read
definitions of TDE and all the other TLA's (Three Letter Acronyms) used
regarding mirrors?

Peder

-----Original Message-----
From: Dan Chaffee [mailto:dchaffee@gvi.net]
Sent: Tuesday, June 22, 1999 2:51 AM
To: Richard Rovelstad; atm@shore.net
Subject: Re: ATM A few questions before I screw my Dob together for the
first time..

> 
> I have used a black marker to darken the edge of the diagonal mirror,
should
> I do the same for the primary?  

Blackening the edge serves one, if not two functions: it hides TDE and
sharpens the minute fuzziness of ground edge bevel to minimize diffraction
effects from the edge. It's best to star test the scope and see if TDE
is present, if so, try varying amounts of masking with a paper annulus.
When you settle on how much edge you need to lose (if any), put the
mirror on a revolving table to apply the black marker. If you try
freehanding it, an unevenness will likely result. Personally, I prefer
a metal annulus for easier maintainance when cleaning the mirror.

D Chaffee