12.5" Moonsilver II
|2nd Place Craftsmanship, 2nd Place Mechanical Design
Ross Sackett's amateur telescope making
- Newtonian design, with custom 12.5” f/5 primary mirror by Ed Stevens,
2.1” m.a. secondary mirror
- 6-point primary cell with four safety bolts RTVed to back of mirror, ±45°
- Curved spider, helical focuser, and red-dot 1X finder
- Variable iris focuser baffle, black velvet-covered Kydex secondary baffle,
hinged protective mirror-box cover held open with rare earth magnet
catch, and black velvet mirror-box deck.
- Total weight is 44 pounds, including optics
- Single-pole UTA support, curved for ergonomic eyepiece position
- 3-point hybrid “fork-dob” altitude bearing for stability, ease of transport,
and friction control
- Teflon-on-Ebony Star bearings; stainless steel bolt altitude and azimuth
axes running through bronze bushings and Teflon and brass washers,
with locking knobs for friction control
- Latch to secure altitude bearing to rocker for transport
- Oak and oak veneered plywood, aluminum tube and spider, multilayered
stain with pore filler and polyurethane varnish
- Carried in and out of doors with one hand with mirror box latched to rocker
- Breaks down for transport in an airline legal check-through bag, ski bag
for pole, with optics in carry-on bag
- Despite single-pole design, flexure and vibration characteristics are similar
to a 12” scope on a convention German equatorial mount; vibrations
damped in 2-3 seconds
- No diffraction spikes visible (a hazy circular diffraction patch is visible
around very bright objects, however)
- Baffling tight enough to be used close to streetlights without noticeable
glare in the eyepiece
- Good friction control for accommodating difference eyepiece weights and
- Eyepiece position comfortable for standing or seated use
- Sculptural appearance more welcome in living room than conventional
Moonsilver II (second from right) was built during
the summer of 2006 in preparation for Stellafane.
The scope is a scaled-up version of the 8"
Moonsilver I had built a month earlier for the
RTMC. Since I had already worked out most of
the mechanical details it took only about three
weeks to build, including time out after a tablesaw
injury making me temporarily left handed (yeah,
don't ask; I can still count in the decimal system).
Stellafane 2006 was a blast! The evening before the competition was
beautiful, and the scope performed gratifyingly well under the dark skies of
The morning of the competition was bright and clear. Despite the stitches in
my right hand I was able to carry the scope single-handed, showing how
portable it really is. Lots of people came by to move it around and to talk
about it (always the best part of a telescope making competition!). The
judges came by in two waves, then for a second time to agree on the order
of the awards.
During the afternoon of the competition Timothy Farris filmed a number of
us with out scopes for his documentary Seeing in the Dark. He had some
complimentary things to say about my scope in the commentary track of the
DVD--another big ego rush for me.
That evening the awards were given out in Flanders Pavillion because the
weather was being very dramatic; tornadoes seemed to be a possibility.
Moonsilver II was awarded second place awards in both craftsmanship and
My telescopes and ATM Projects