Keck Observatory Technical Note 163
Jerry Nelson
7 January 1986
Revision 1 19 May 1988
Revision 2 18 July 1989
Revision 3 24 June 1991
File: Optical Parameters R3
����������� The completion of a set of 6 segments at Itek has occasioned a slight change in the radius of curvature of the primary mirror which is included here. We do no not expect that the primary mirror parameters will change any further. These values and those given for each of the segments are the same as those given in a previously distributed note dated 17 April 1989. Included in this note are segment descriptions for both the final segment with a = 0.9m and for the uncut mirrors with a = 0.95m.
����������� The f/15 secondary is in the process of fabrication. To minimize the material removal during aspherizing of the secondary, the radius of the curvature of the f/15 secondary has been changed slightly. This is included below. The indicated values are similar to those given by Epps in a 14 March 1989 letter, and extremely close to those given to me by Epps in a 13 July 1989 telephone conversation. The radius of curvature of the secondary may still change somewhat during the fabrication process (up to 70mm, probably substantially less) so these parameters are not final.
����������� In this third revision, I have added the radius of curvature of the focal surfaces. This was inadvertently left out in the last version. For f/15 and for f/25 the focal surface is concave as seen from the secondary. I have also made a few minor format clarifications that were inadvertently omitted in the version sent to you a week ago.
Calculate parameters defining telescope optical surfaces (created 30jan89, last mod 24jun91) not quite a Rithey-Chretien system at f/15. (independently defined primary)
Radius of Curvature | k(m)� | 34.9740 |
Primary mirror dia. | DP(m) | 10.949 |
Primary conic const | CC | -1.003683 |
f/15 Secondary Parameters
Back focal distance | e(m) | 2.5000 | del | 0.14296334 | 2e/k |
Final focal length | f(m) | 149.583 | m | 8.55394865 | 2f/k |
Primary-sec. Dist | d(m) | 15.394985 | |||
Sec. Rad. Of Curvature | k2(m) | -4.737916 | |||
Sec. Conic const. | SCC | -1.644326 | |||
Focal radius of curv. | 1/km (m) | 2.123573 | |||
f/15 FOV radius | FV1 (�) | 10.00 | |||
Secondary dia 0� FOV | DS0 (m) | 1.309857 | |||
Secondary dia inc FOV | (m) | 1.399421 | |||
Coma at 10� radius | ATC (�) | -0.005 | |||
Astigmation at 10� radius | AAST (�) | 0.506 | |||
Field size for 20� FOV | (m) | 0.870 |
f/25 Secondary Parameters
Back focal distance | e(m) | -4.538 | delp | -0.2595071 | 2e/k |
Final focal length | f(m) | 250.000 | mp | 14.2963344� | 2f/k |
Primary-sec. Distance | d(m) | 16.640457 | |||
Sec. Rad. Of curvature� | k2(m) | -1.820420 | |||
Sec. conic const. | SCC | -1.418029 | |||
Focal radius of curv. | 1/km (m) | 0.808794 | |||
f/25 FOV radius | FV1 (�) | 5.00 | |||
Secondary dia 0� FOV | DS0 (m) | 0.530039 | |||
Coma at 5� radius | ATC (�) | 0.690 | |||
Astigmatism at 5� radius | AAST (�) | 0.233 | |||
Field size for 10� FOV | (m) | 0.727 |
a(m) | 0.9 | ||||
Segment Type | Type 1 | Type 2 | Type 3� | Type 4,5 | Type 6 |
R(m)(oad)� | 1.55885� | 2.70000 | 3.11769 | 4.12432 | 4.67654 |
R/k (ep) | 0.04457156� | 0.07720021 | 0.08914312 | 0.11792526 | 0.13371468 |
cc*ep^2 | -0.0019939 | -0.0059818 | -0.0079758 | -0.0139576 | -0.0179455 |
1-cc*ep^2 | 1.001994 | 1.005982 | 1.007976 | 1.013958 | 1.017945 |
Zernike Coefficients of Segments (microns)
C20 | 5778.499 | 5755.625 | 5744.265� | 5710.485 | 5688.212 |
C22� | -11.505 | -34.310 | -45.611 | -79.114 | -101.122 |
C31 | -4.419 | -7.572 | -8.695 | -11.318 | -12.695 |
C33 | 0.007 | 0.034 | 0.052 | 0.118 | 0.170 |
C40 | 0.001 | 0.004 | 0.006 | 0.012 | 0.015 |
C42 | 0.002�� | 0.006 | 0.007 | 0.013 | 0.016 |
C44 | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 |
Primary Segments
a(m) | 0.95 | ||||
Segment Type� | Type 1� | Type 2 | Type 3� | Types 4,5 | Type 6 |
r(m) (oad) | 1.55885� | 2.70000 | 3.11769� | 4.12432 | 4.67654 |
r/k (ep) | 0.04457156 | 0.07720021 | 0.08914312 | 0.11792526 | 0.13371468 |
cc*ep^2 | -0.0019939 | -0.0059818 | -0.0079758 | -0.0139576 | -0.0179455 |
1-cc*ep^2 | 1.001994 | 1.005982 | 1.007976 | 1.013958 | 1.017945 |
Zernike Coefficients of Segments (microns)
C20 | 6438.389 | 6412.905 | 6400.248 | 6362.613 | 6337.798 |
C22 | -12.818 | -38.226 | -50.816 | -88.144 | -112.663 |
C31 | -5.198 | -8.905 | -10.227 | -13.311 | -14.931 |
C33 | 0.008� | 0.040 | 0.061 | 0.139 | 0.200 |
C40 | 0.001 | 0.006 | 0.008 | 0.014� | 0.019 |
C42 | 0.002 | 0.007 | 0.009 | 0.016 | 0.020 |
C44 | 0.000� | 0.000� | 0.000 | 0.000 | 0.000 |
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