Galaxy Optics is at the high-end of quality for large thin
mirrors for Dobsonians. You'll find them in JMI's NGT scopes,
Obsessions, StarSplitters and others.
The mirror was made in May 1995 as SN-01462 and was figured by
The optics set here consists of a 22" precision-annealed pyrex mirror, 99.1" FL, 2" thick, with 96% coatings and weighing 72lbs. It has full laser interferometry, and shows wavefont astigmatism of 1/45 wave, and spherical aberration averages 1/15 wave on the wavefront!!
The integrity of the coatings is excellent. However, there are
mini-scratches from cleaning.
The diagonal is 3.5" for a minimal 16% (!) obstruction. This very
small obstruction requires particular care in choosing and placing
your focuser. (You want the separation between the focal plane at
the outside of the fouser and the center of the diagonal mirror to be less than 13 7/8" -- this requires using a very low profile focuser, or embedding the focuser into the tube slightly, or both. --A small price for optimal contrast). Interferometry on the diagonal shows 1/11 wave P-V on the surface. It has 97% coatings.
The current cost of this set from Galaxy is $5505. Because of
illness I can no longer use the telescope containing them, so
they are available for $4000 + US shipping.
This is an outstanding price on some outstanding Newtonian optics!
:-) Contact the seller for further details.