[Last Change: 05 Apr 2011 (rev 2)]
ACIS-S Plate Focus Analysis: Obsids 00047, 00062, 00069, 00070, 00071
Eli Beckerman, Olivia Johnson (3/31/00)
The latest ACIS-S plate focus observations, taken to check for variation since launch due to out-gassing by the optical bench, indicate that the best focus position remains essentially unchanged.
Five observations of PG1634+706 (obsids 47, 62, 69, 70, 71), taken at defocus of -0.25, -0.1, 0.0, 0.1, and 0.25 mm, respectively, were analzyed using the standard
plate focus routine. Exact defocus values were read from the FITS header of each image. The analytic fit to the autocorrelation function values yields a best focus which is offset -0.025 ± 0.035 mm (-17 ± 24 motor steps) from the value in the ODB. This corresponds to a best focus that is -0.966 mm (-658 motor steps) from the launch-lock position, and -0.710 mm (-486 motor steps) from the mechanism's zero point.
| OBSID |
Defocus (mm) |
Offset from Launch-Lock (mm) |
ACF value |
| 00047 |
-0.2431 |
-1.1829 |
0.616 |
| 00062 |
-0.0966 |
-1.0364 |
0.660 |
| 00069 |
0.0014 |
-0.9383 |
0.693 |
| 00070 |
0.0999 |
-0.8399 |
0.644 |
| 00071 |
0.2452 |
-0.6945 |
0.569 |
