It's also just barely hyperboloidal, but Steve said that the amount of over-correction wasn't enough to make any difference in use. On Tue, Oct 22, 2013 at 8:35 AM, Hutchings, Mat <mat.hutchings@siemens.com>wrote:
The mirror did not require any figuring, which was a great relief to Mike. The mirrors figure was discovered only after the mechanical part of the telescope was complete enough to put the mirror in and test it. So by then, he was very committed to the project.
They did find that the central part of the mirror is not corrected, but this is not a big deal as it is in the shadow of the large secondary. Perhaps the lack of correction was due to the fact that whatever cameras/instruments were to be installed on the original spy telescope would "shade" that part of the mirror.