Re: [ATM] TDE

["Bob May" <bobmay@nethere.com>]

The question is how much TDE and how strong it is.  If the TDE is wider, the
amount of area is larger, making for more of defocused image.  The larger
the ROC increas, the larger the blur.  Of course, the rest of the mirror's
quality is dependent upon how good the focus point is.
The biggest thing that I've seen is that bright stars will have a small blur
around them with a bit of a TDE.
Often the quick "cure" for the TDE on a mirror is to mask it off or grind
the edge to eliminate it.  In each case, you have a slightly smaller mirror
and if you grind it off, the Twyman effect will lift the edge which will
compensate for the last little bit of TDE that may remain.
Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net
----- Original Message -----
From: Ajnabiyar <ajnabiyar@yahoo.com>
To: <atm@atmlist.net>
Sent: Wednesday, July 13, 2005 2:48 AM
Subject: [ATM] TDE


> Hello,
>
> If slight/modest TDE is left in the mirror, what does it make a difference
on the sharpness of the image.
>
> Ajnabi
>
>
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