From: "Martti Koskimo" 
To: 
Reply-To: "Martti Koskimo" 


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This is very much true.

The Quality of the diagonal, if it is located at the objective( mirror), =
needs to be the 'same' as the main mirror tolerance. This tolerance is =
reduced to the same as the focus tolerance at focal plane. Between these =
extreme points the tolerance change is 'linear'. For very long focal =
length mirror the diagonal tolerance is say 1/4 wave at the objective = and
can be millimeter range at the focus.

If there is general curvature in the diagonal the situation is more = complicated.

Martti Koskimo



  ----- Original Message -----=20
  From: Richard Schwartz=20
  To: atm{at}shore.net=20
  Sent: Tuesday, April 01, 2003 1:04 AM
  Subject: ATM How Good Does a Diagonal Need to Be?


  I am wondering if the quality required in a diagonal depends on the =
distance from the diagonal to the focal plane.   If the diagonal is very =
close to the focal plane, perhaps error in the diagonal surface can't do =
much damage....

  . . . Richard

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This is very much true.The Quality of the
diagonal, if it =
is=20
located at the objective( mirror), needs to be the 'same' as the main = mirror=20
tolerance. This tolerance is reduced to the same as the focus =
tolerance=20
at focal plane. Between these extreme points the tolerance change is =
'linear'.=20
For very long focal length mirror the diagonal tolerance is say 1/4 wave = at the=20
objective and can be millimeter range at the focus.If
there is = general=20
curvature in the diagonal
the situation is more=20
complicated.Martti
Koskimo

  ----- Original Message
----- 
  From:=20
  Richard=20">mailto:richas{at}earthlink.net">Richard=20
  Schwartz 
  To:
atm{at}shore.net">mailto:atm{at}shore.net">atm{at}shore.net 
  Sent:
Tuesday, April 01, 2003 =
1:04=20
  AM
  
Subject: ATM How Good Does a =
Diagonal=20
  Need to Be?
  
  I am wondering if the quality =
required in a=20
  diagonal depends on the distance from the diagonal to the focal=20
  plane.   If the diagonal is very close to the focal plane, =
perhaps=20
  error in the diagonal surface can't do much damage....
   
  . . .=20
Richard

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