magnilux - Astronomy Technology Today

The
“Home Depot”
Keeping
It Simple
Scope
By Jack Fenimore
Image 1a-1c: The scopes simple 3-truss, dual-tube design yields a simple-to-construct, lightweight, and stable Dob.
The Plan
Observing conditions at my home
near Albany, New York – overcast some
nights and mediocre seeing in Magnitude-
4 skies the others – have caused me to
spend most of my time observing solar-system
objects, star clusters, and double stars.
My trusty Tele Vue 102 Apo on a Losmandy
GM8 mount has proven to be a superb
instrument for skies that limit
resolution more than does that scope’s four
inches of aperture.
But for those rare clear nights with
high transparency, I wanted more light. I’m
in pretty good shape for a senior citizen,
but I wanted a telescope optical tube assembly
(OTA) that I could pick up with
one hand while carrying the mount with
the other. The OTA would have to: fit in a
Toyota Corolla without need for disassembly
(for simplicity of construction) when
transporting to a local “dark-sky” site; not
be sensitive to balance; be able to lie on the
grass without rolling over onto the finder
or focuser; require only simple power tools
for construction; and use materials readily
available at the local Home Depot.
I had planned to build an 8-inch Dob
until I discovered conical mirrors made
by Bob Royce. Their optical reputation
was excellent and their weight was considerably
less than conventional-thickness
flat mirrors. A 10-inch was therefore a
possibility.
Bottom line: after investing three
weekends on the project, I was enjoying
observing with a ten-inch reflector that
meets all the requirements listed earlier, has
an OTA weighing only 27 pounds (not including
the finders), and a mount weighing
15 pounds. The only power tools used
in its construction were a hand-held saber
saw and drill.
The Components
Components for this project included:
the 10-inch conical f/6 mirror from Royce,
a 1.83-inch quartz secondary with mount
from ProtoStar, focuser from JMI, finders
from Telrad and Orion, Ebony Star laminate
from Meridian Telescopes, a fan and
rechargeable battery from Radio Shack,
and materials for tube and mount from
Home Depot. The mirror mount was
made of wood, but if I were starting the
project today, I would probably use a conical
mirror cell from Optical Supports.
Astronomy TECHNOLOGY TODAY 63