; From Ian Evans 12/21/96:
hsi_pixel = 6.42368  ; stage Y microns / HSI pixel
hsi_angle = -0.5181  ; degrees

; where the rotation angle sign convention is given by this example:
; (IDL code example)
rads = hsi_angle * !DTOR
facility_Y = hsi_Y*COS(rads) - hsi_Z*SIN(rads) 
facility_Z = hsi_Y*SIN(rads) + hsi_Z*COS(rads) 

; Nominal aim point (~ HSI center?) definition:
; These are in the pixel coordinates of the 2nd floor event files,
; e.g. of the form "hsi<runid>i<iteration>.fits
hsi_Y_aim = 2048
hsi_Z_aim = 2048