Sky & Telescope - January 2021 - 74

ASTRONOMER'S WORKBENCH by Jerry Oltion

The
Trekking
Pole Travel
Scope
Never leave home without it!
ON A TRIP TO SOUTH AMERICA a year
or so ago, Washington, DC amateur
astronomer Robert Capon made the
decision to travel light, leaving his
portable telescope at home. That proved
to be a mistake, as the southern sky was
spectacular, but all he had to appreciate
it with was his 8×42 binoculars.
He did take his Ruta Locura Yana
carbon-fiber trekking poles, though, and
while hiking under that beautiful sky
he began to wonder if he could design a
travel scope that would use the trekking
poles for struts. He says, "The goal was
to design and build a portable telescope
that would be rugged, and so small and
light that I would never be tempted to
leave it behind."
He settled on a 114-mm (4½″) f/4
mirror, which just fit into a Pelican 1120
Protector Case. That turned out to be an
ideal housing. It's lightweight yet very
rugged, and the plastic is easy to drill
and shape with a
Dremel tool, plus it
holds screws well.
The inside is filled
with pluck foam,
which is perfect for
custom-fitting cavi-

S Robert Capon carries his ultra-compact,
ultra-lightweight travel scope.

ties to protect all the parts in transit.
Mounting the trekking poles was
fairly straightforward. Rob carved two
channels out of the lip of the Pelican
case just inside the handle. That provided 2.6″ of spacing between the poles
and allowed the use of the handle supports for additional stability. He secured
the poles in place with hose clamps.
The mirror cell uses the Pelican case
itself for its rear element and three
drilled and countersunk wooden squares
for the mirror's support points. Panhead bolts are glued to the wood, and
the squares are glued to the mirror. Bolts

run out the back of the case for collimation. Springs around the screws keep
the mirror firmly in place, although Rob
added lock screws as well by drilling
and tapping the Pelican case.
He wanted everything but the poles
stored in the case, which meant going
with a minimalist focuser. Some rummaging around in his astronomy parts
box turned up a Celestron 1.25″ visual
back, which he mounted upside-down
on a ¼″ plywood square. The visual
back threads were cut off to lower the
focuser's profile. That holds the eyepiece
securely, and focus is achieved by simply
loosening the set screw and moving the
eyepiece in and out. If the focal point
is outside the eyepiece's travel range,
the truss lengths can be adjusted where
they attach to the Pelican case.
The secondary mirror is on a single
stalk that bolts to the wooden focuser
platform. Rather than clamp the trekking poles on the upper end, Rob added
two 6″ lengths of carbon fiber rod that
slip snugly inside the ends of the trekking poles, so the entire assembly can
be slid into place in a moment using
trekking pole splice joints. With the
secondary removed, the focuser/secondary assembly also fits into the lid of the
Pelican case, with the secondary mirror
tucked in beside it. A trimmed spindle
case for a 50-pack of DVDs makes a fine
protector for the primary mirror.
Rob mounted a finder bracket to the
side of the case and uses a low-profi le
red-dot fi nder so it will fit in the case
along with everything else. There's just
enough room for a 25-mm eyepiece

XX Everything but the
trekking poles and tripod
fits inside the Pelican
case.

74

JANUARY 2 021 * SK Y & TELESCOPE

ROBERT CA PON (4)

X The travel scope sets
up easily and provides
an excellent observing
experience.



Sky & Telescope - January 2021

Table of Contents for the Digital Edition of Sky & Telescope - January 2021

Contents
Sky & Telescope - January 2021 - Cover1
Sky & Telescope - January 2021 - Cover2
Sky & Telescope - January 2021 - 1
Sky & Telescope - January 2021 - Contents
Sky & Telescope - January 2021 - 3
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Sky & Telescope - January 2021 - Cover3
Sky & Telescope - January 2021 - Cover4
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