RE: [ATM] Is this Sphere good enough?

["Jerry" <wa4guu@verizon.net>]

The perfect sphere is aberration free with regard to an object (point
source) at the center of curvature of the mirror. The discussion started
with "is the sphere good enough?" and he was describing the quality of the
sphere. I would not worry about the Strehl of the sphere that I put on a
mirror before parabolizing but he did not know how good he needed so he
added that info regarding the quality of the sphere he has.
Also consider that the quality of a lens could stated as a Strehl ratio. A
parabola is not necessary. Or think of a microscope objective that will
focus on a one millimeter distant object rather than infinity. The distance
of intended focus impacts on the Strehl of the lens or mirror.

Jerry 

-----Original Message-----
From: Vladimir Galogaza
 
Don Ray wrote:

>I ran FIGURE using a 5 zone mask with a Sphere as the
reference with the following results:
P-V Error - 1/2.75
Strehl Ratio - 0.825
Surface RMS Error - 19.3
against a Parabola I get the following:
PV Error 1/1.25
Strehl Ratio 0.054
Surface RMS 63.5

I thought that concept of the Strehl (ratio) is clear to me.
Reading Don's post and some answers I realized That I am wrong.

While I thought that Strehl of the aberrated mirror is defined as
the ratio of the peak intensity in the image of the infinite far point
source
of the aberrated mirror to the
MAXIMUM possible peak intensity in the image of the same source
as produced by the mirror of the same diameter and the same (?)  paraxial
radius
of curvature
(which is -1 conic or ideal paraboloid).




Vladimir.


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