FOCUS PYRAMID
The distance "d" between the four outlying images produced by the
focus wedge and the central image and the telscope defocus "f" are
linearly related by d=a+b*f. Errors in the co-efficients are in
brackets.
| Date\Coefficients | a | b |
| December 1997 | 35.2 | -15.4 |
| March 1998 | 35.1 | -14.4 |
| May 1998 | 35.1 | -16.4 |
| July 1998 | 34.95 (0.12) | -15.5 (0.5) |
| August 1998 | 35.21 (0.09) | -16.8 (0.4) |
| September 1998 | 35.11 (0.11) | -14.9 (0.4) |
| January 1999 | 35.05 (0.10) | -14.9 (0.3) |