Re: [ATM] Recognising TDE

["Mike Spooner" <spoon@PageAmerica.net>]

Mike, James and all,

Here is a photo of a mirror with a TUE. This site has popups, cookies and 
ads so have your blockers working.
http://www.mikespooner.50megs.com/8inf6.htm

 I've only seen a few mirrors with  real TUE but they do happen 
occasionally.

--Mike Spooner

----- Original Message ----- 
From: "Mike Lockwood" <melockwo@uiuc.edu>
To: <atm@atmlist.net>
Sent: Tuesday, November 08, 2005 9:25 AM
Subject: Re: [ATM] Recognising TDE


> James,
>
> James Mulherin wrote:
>> Any way, here goes. A TDE spreads light radially outward from the star's
>> image causing spikes and causing loss of contrast. On the other hand, a 
>> TUE
>> causes light to come to focus ahead of the light coming from the good 
>> part
>> of the mirror. In fact, this light crosses the focus point and then
>> continues on radially outward. I suspect that the effect of a TUE is
>> essentially the same as a TDE, although I doubt that anyone could produce 
>> in
>> a TUE the kind of extremely steep slope that can be produced in a TDE.
>>
>> Can any one else comment on this. Is a mild TUE effectively the same as a
>> mild TDE in the star test?
>
> A point of terminology - I define the edge as the outer ~1/16" of the
> mirror, and I have never seen a true TUE by this definition.  However,
> I have seen plenty of "turned up outer zones", or undercorrected outer
> zones, 1/4" and wider.
>
> James, you've made more mirrors than me - ever seen a true TUE by that
> definition?
>
> You might try the "Star Test" feature of FigureXP to simulate the star
> images of a mirror with a narrow undercorrected outer zone.
>
> A turned up outer zone will often masquerate as a good outer zone when
> the mirror is cooling!
>
> Mike Lockwood
>
>
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> 


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