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MN66 Mirrors' Reflectivity

Started by Kimballcorson, 05/08/2003 03:33PM
Posted 05/08/2003 03:33PM Opening Post
A brief while ago, I posed the question
on another forum of what is the reflectiity
of the MN66 mirrors, 91-92%, as a few dealers
advertise, or 95-96%, as most world-wide
dealers state. I heard from many. After
studying the primary, getting feedback and
canvassing dealers world wide, the consensus
seems to be reflectivity on the MN66 is
95-96%. As a couple of dealers pieced it
together, Intes came out with the MN61 first
and used no baffling, Pyrex for the primary,
91-92 % coatings, a smaller tube diameter,
a heaverier tube assembly, and no vents in
the bottom. The scope was a big hit. Orion
even picked it up for distribution under its
own name. Subsequently, when Intes Micro
decided to produce a 6" Mak-Newt, as a
renegade spin off company from Intes, they
wanted to one-up the Intes MN61 and did so
by adding extensive baffling along the tube
and smaller baffling across from the eyepiece
holder, enlarging the tube diameter to allow
for all this new baffling, lightening the
tube assembly at the same time, using Sital
substrate for the primary mirror instead of
Pyrex, using Russian BK7 for the secondary
mirror, adding vents at the base of the
primary to accelerate cool down, etc.
Because of the upgraded and enhanced mirror
materials, coatings were also upgraded to
95-96% reflectivity on both mirrors and care
was taken to increase wavefront p.t.v. to
about 1/7.5 to 1/8 on average, although
1/6 is typically advertised, to be safe
and catch the ocassional Russian Q.C.
slippages. Thereafter, Intes reacted to the
MN66 by offering a Deluxe version of their
MN61 which, among other features, also
offers enhanced coatings with 95-96%
reflectivity and better wavefront figures
than the standard model MN61. Those are
presently the offerings in the world market
place from Intes and Intes Micro for a
6" F/6 Mak-Newt.

Kimball Corson