Fundamental parameters are in bold text, other parameters are derived.

PARAMETER	IN INCHES	MILLIMETERS	Comments
f/2.07 PRIMARY MIRROR
Diameter of front face	93.0	2362
Clear aperture (after masking)	91.5	2324
Thickness	9.2	234
Diameter of central perforation	12.0	305
Weight	4400 lb	2000 kg
Paraxial radius of curvature	379.24	9632.7
Sagitta	2.86	72.6
Conical constant (dimensionless)		-1.05015	E&F'97 use -1.050145
f/7.5 SECONDARY MIRROR
Diameter of front face	26.625	676.3
Illuminated diameter of front face	26.0	660
Secondary baffle outside diameter	29.25	743
Thickness	3.125	79.4
Paraxial radius of curvature	130.263	3308.7	E&F'97 use 3308.68 mm
Conical constant (dimensionless)		-3.54396
Prime focus intercept	47.64	1210
Vertex separation of mirrors	141.98	3606.3	E&F'97 use 3608.98 mm
Back focal distance (mechanical)	35.4	899
Back focal distance (optical)	35.21	894.3
Back focal range (optical)	+0.35 to -0.25	+8.9 to -6.3
Final focal ratio		f/7.31	from E&F'97
Paraxial image scale		0.0864	in mm/arcsec, from E&F'97
Inverse image scale		11.50+-0.005	in arcseconds/mm
Focal surface curvature radius	49.64	1261	from E&F'97
Unvignetted field diameter	4.9	125	value in Manual
Unvignetted field diameter	7.2	182	calculated value

The unvignetted field diameter calculated from the diameter of central perforation, the f-ratio and the back focal distance is 182 mm. The baffle behind the primary is somewhat over 11 inches in diameter, near the front surface of the primary (according to Bob Barr, 25 Nov. 1998), which would produce an unvignetted field diameter of about 6.3 inches, or 160 mm. The value in the Manual by Mack et al. appears to be the limit imposed by the entrance aperture of the old MIS.

Note that the Mack et al. and E&F values for the image scale differ by 0.6%.