Sky and Telescope - July 2017 - 72
ASTRONOMER'S WORKBENCH by Jerry Oltion
How to point out the obvious.
use the Sun as part of the system. You
can either cast a shadow onto a target
or cast a beam of light on a target.
The simplest ﬁnder I've seen consists
of two tabs of masking tape. Stick one
on the front edge of your scope with an
inch-long tab standing out. Put another
tab a foot or two back, in line with the
one on the front. Poke a hole in the
middle of the front tab, and move the
scope around until the ray of light shining through the front tab hits the back
tab. Center it up, and you're on target.
Cut the front tab into an arrow
shape with its point half as high as the
rear tab and you get the same effect
with a shadow instead of a bright spot.
Masking tape isn't very elegant, and
it's hard to get the two tabs precisely
aligned. You're better off building a
p This folding finder casts a bright spot on a frosted screen. The front element shades the screen,
and sunlight shines through the hole.
J U L Y 2 0 1 7 * SK Y & TELESCOPE
p David Lazaroff made this Sun finder from a
detergent jug spout.
ﬁnder that you can mount solidly on
your scope so it'll remain aligned from
use to use. Designing it to ﬁt on your
regular ﬁnder's mount is a good strategy, since you won't be using that ﬁnder
by day anyway.
A 4- or 5-inch length of 1-inchdiameter PVC pipe makes a good ﬁnder
body. Cap the front end and drill a
small (1/16-to-1/8-inch) hole in the middle
of the cap, then stretch a section of
white plastic bag across the back. When
aimed at the Sun, a bright spot of light
shines on the white plastic. After you've
found the Sun in the scope for the ﬁrst
time with the ﬁnder attached, put a
black dot in the center of the bright spot
with a felt marker and you'll have no
trouble ﬁnding the Sun again.
One nice variant is to open the body
of the ﬁnder so you can look at the
bright spot on the screen from above.
That eliminates bending down to see
it. I made the ﬁnder at left from two
pieces of ﬂat PVC plastic and a piece of
clear Plexiglas, which I frosted with ﬁne
sandpaper to make a screen. The upright
TOP: DAVID L A Z A ROFF; BOT TO M: JERRY OLTION
LAST MONTH I wrote about making
your own solar ﬁlter. Now you're all set
to look at the Sun, right? So how do you
aim your scope at it?
Come on, how hard can it be? It's
right there, big and bright and half a
degree acro. . . ss. Oh. Yeah. It only
covers half a degree of sky. And it's too
bright to look at with your Telrad or
optical ﬁnder. (Seriously, don't do that.)
The Sun is too bright to even sight
down the your telescope's tube at safely.
With the ﬁlter on your scope, you won't
see any glow through the eyepiece until
you're right on it. Until you've tried it,
you'd be amazed at how difﬁcult it is
to aim a telescope at the Sun without
some kind of ﬁnder.
Here's how to make one.
There are two basic ways, and both