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)