ASTRONOMER’S WORKBENCH by Jerry Oltion
Better Balance Weights
Fine-tune your scope’s balance with these simple weights.
LIGHTWEIGHT TELESCOPES are a
joy to use, but they have one common
drawback: The eyepiece contributes a
signifi cant fraction of the scope’s total
weight. And eyepieces range anywhere
from a couple of ounces to a couple of
pounds, so when you fi nally track down
an elusive planetary nebula and remove
your wide-fi eld eyepiece to switch to
a higher power, the unbalanced scope
often takes off for the zenith, undoing
all your work.
In our November 2016 issue I
described a disk brake system for
locking down a scope while changing
eyepieces, but New Hampshire ATM Joe
Dechene has developed a simpler, more
versatile way of accomplishing the same
thing: adjustable weights.JOE^ DECHENE(^4
)74 AUGUST 2019 • SKY & TELESCOPE
Moveable weights are nothing new,
but Joe’s implementation of them is the
most user-friendly I’ve seen. He didn’t
need to screw any rails to his telescope,
and he doesn’t need to loosen any lock-
ing screws to slide a weight forward or
back. He simply attaches the weights to
his telescope’s trusses, where they can
be moved up and down as necessary.
If I were designing such a system, I
would have stuck long strips of Velcro
hooks on the trusses and put some
loops on the weights, but that’s why
I’m writing about Joe’s design and not
mine. Joe realized that tugging Velcro
loose and sticking it back down would
knock a telescope off target just as eas-
ily as changing an eyepiece (not to men-
tion there’s the danger of dropping a
weight on the primary while attempting
to move it). So he came up with a better
way. The hooks go on the weights, and
the loops go on the ends of stiff elastic
bands. When you wrap the elastic
around the trusses and stick the Velcro
together, the weights can be slid up and
down the trusses smoothly and easily
without disturbing the scope’s aim.
The weights can be constructed of
pretty much anything heavy. To make
them easy to grip and slide, Joe used
¾-inch-square steel bar stock. In order
to prevent damage to the primary mir-
ror if he did accidentally drop one, he
put soft wooden caps on either end.
On the sides he made curved wooden
surfaces that match the truss diameter,
with^11 / 1166 -inch hobby foam lining the
inside of the curve so the wood doesn’t
contact the truss poles directly.
Joe reports that “Operation cannot
be easier. Simply attach to the truss
poles as needed and slide to compensate
for various eyepiece or camera weights.
It’s a joy to use, being easy to slide and
precisely balance the scope.”Balancing the scope in all positions
between horizon and zenith may require
weights on more than just one truss, so
make a couple while you’re at it.
That solved the problem nicely for his
truss-scope. But what about his equa-
torially mounted refractor? He could
set the initial balance on each axis by
counterweight position and dovetail
position, but he still had the same prob-
lem when he removed a heavy wide-fi eld
eyepiece to put in a lightweight high-
power eyepiece. Trouble was, there were
no trusses to mount weights to.
The solution was a drawtube weight.
Joe made a U-shaped weight with two
pieces of the same steel bar stock hepJoe Dechene’s adjustable weights attach
tight to the telescope’s trusses, yet can be eas-
ily slid up and down to fi ne-tune the balance.pTop: Velcro hooks go on the weights, and
loops on the elastic straps. Curved contact
surfaces lined with hobby foam ensure a snug fi t
against the telescope’s trusses. Bottom: Each of
the weight components is laid out for assembly.