From: "William Podgorski" 
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Date: Fri, 1 Sep 1995 14:00:43 -0400
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Subject: Preliminary Calcualtions of TMA Grating Position
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I ran some raytraces of the TMA mirror using OSAC parameters which I received
from Jack Hughes. The coordinate system used is the OSAC system, with
the Z = 0.0 plane located at the WIDE end of the P. I ran both infinite
and finite source cases. The finite source distance was assumed to
be 1744.6 ft(531,754mm). This places the centerline of the TMA approximately
14.6 ft WEST(away from the fource) of the Pier "2" centerline, which is also
the HRMA centerline. This is per Ed McLaughlin's sketch of the TMA
installation. The grating plane is placed 5000 mm from the finite
source focal plane, thus resulting in an avg ray ring diameter of 349.1 mm.
The shutter plane is assumed to be ~546 mm from the TMA mid-plane, as
installed before. The avg ray ring diameter at the shutter plane is 385.58 mm.

Axial Station            Infinite Source  Finite source   Ray Ring Diameter
(mm from wide end of P)   (for ref only)
X-ray Point Source           -Infinity    -531754    mm
Wide end of P                  0.00 mm          0.00 mm
Center of P                  180.26 mm        180.26 mm
Narrow end of P              360.52 mm        360.52 mm
P/H Midplane                 400.94 mm        400.94 mm
Wide end of H                441.37 mm        441.37 mm
Center of H                  621.60 mm        621.60 mm
Narrow end of H              801.82 mm        801.82 mm
Shutter Blade Plane            N/A            947.00 mm        385.58 mm
Grating Plane                  N/A           1469.55 mm        349.10 mm
Focal Plane                 6400.58 mm       6469.55 mm

William A. Podgorski                Harvard-Smithsonian Center for Astrophysics,
                                       Smithsonian Astrophysical Observatory
Email:   60 Garden Street, MS 5
Phone: 617 495 7363                 Cambridge, MA  02138
FAX:   617 495 7098                 USA