Sky & Telescope - December 2021 - 75

A thick O-ring
on either side
prevents the shaft
from turning independently
from
the ball. Cover
the rod's exposed
threads with a
plastic hose.
Get Globular
easily make them with barbell weights
or even concrete-filled plastic bottles.
Remember the principle of leverage:
The longer the shaft the less weight you
need - but the more awkward it will be.
You can cover the exposed rod threads
with a length of garden hose or any
kind of tubing that fits.
The ball needs to sit in a socket of
some sort that will let it glide smoothly
in any direction. I've heard of people
using dog bowls, but Brett found that a
4-inch pipe end cap works even better.
The bottom is nice and flat and can be
mounted atop a tripod with the equatorial
head removed. Felt pads on the edge
of the pipe cap allow the ball to move
with a buttery-smooth " Kriege and
Berry " feel.
Brett at first mounted the pipe
cap directly atop the tripod head, but
the unbalanced ball/weight assembly
hopped off the pipe cap without the OTA
attached. So he offset the pipe cap sideways
between two of the tripod legs and
cut a slot in the side of the cap so the
counterweights can hang straight down.
That lets him set the ball and weights
into the socket, then set the scope into
the tube rings and close them up with
ease. Once the scope is in place, he's balanced
and ready to observe.
What do you gain by making this
conversion? As Brett says, " There are
some nice improvements in ergonomics
and utility. " No Dob's hole, for one.
Nor any gimbal lock near the North or
South poles. Easy eyepiece height adjustment.
Smooth, single-axis tracking in
any direction. Until you've tried a ball
mount, you have no idea how userfriendly
the observing experience can be.
¢ Contributing Editor JERRY OLTION is
convinced that once people recognize
the simple elegance of ball mounts,
they'll eventually come 'round.
Round out Your Collection of S&T Globes!
Mercury
See also our eclipse globe
(not pictured), showing
all total and hybrid
eclipses this century!
Earth
Celestial
Mars
Mars
Topo
Moon
Topo
Venus
Moon
Each has labels of surface features and uses actual hi-res imagery.
Own all eight S&T 12˝ globes! $99.95 each (except topos, $109.95)
shopatsky.com
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Sky & Telescope - December 2021

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