Evening star., 1933-10-31
HARVARD PREPARES
HUGE OBSERVATORY
Astronomical Camera Is First
of Kind to Be Set ON Ball
Bearings.
Dispatch to The Star.

HARVARD, Mass, October 81
(N.AN.AD.-Har College has an
astronomical observatory which is not
at Harvard College. Yet it is in Har-
ward, for it is at Oak Ridge, in the
town of Harvard.
The observatory has dome for its
biggest telescope, which is not dome.
Inside, one of the biggest telescopes in
the world is being assembled. 1t does
rot telescope. 1t has a tube which
is not a tube. and a lens which is
rot lens. The observer may look
through it or at it: he may sit at the
upper end of the tube and look down.
or at the lower end and look up, or
at one side and look IN.
In its use the telescope is not a
telescope, but camera. In fact, all
the astronomical telescopes actually
used for the study of astronomy now
adays are cameras.
The soul of the telescope, as DR..
Harlow Shapley, the director, said. is
the polar axis This is massive shaft
of steel which revolves in two great
sleeves, or journals The journal
boxes are bolted on the two Slanting
piers of concrete in the pit. If it is
rightly placed. the shaft will point di-
rectly at the North Star.
Tons Moved Hairs Breadth.
There are adjusting screws to cor
rect any error. and here is one of the
marvelS of this great instrument. The
shaft weighs tons; on it is hung
base that weighs almost as much; the
tube" weighs about tons; the mirror
which is referred to as the lens-the
circles and the other gadgets that go
to make up the telescope bring the
total weight to 80 tons or more. To
the layman it is incredible that such
a mass can be moved to one side or the
other. or skeWed around at hair
lines difference OF angle by any screws
that can be manipulated by human
hands. Yet it is so.
There is another phase of that "po-
lar axis In its two journal boxes
are sets of ball bearings. what are
the great gun mounts. The bearings
weigh 400 pounds apiece and cost more
than $4,000. They are accurate down
to fractions of a thouSandth of an
inch.
The whole weight of the telescope
rests on these bearings, but they must
turn the axis in a true, unvarying
'cisle when the shaft is turned.
This is the first big telescope in the
world that ever was mounted on ball
bearings. The other great telescopes,
like that at Mount Wilson, are floated
in mercury. The mercury is only
film a thousandth of an inch thick.
But heretofore. nobody believed any,
thing else could give an accurate turn.
On the upper end of the polar axis
Is to 90 the great fork between the
horns of which the telescope is to be
swung. In similar fashion, the new
61-inch telescope will be swung, with
a base" at its lower end. a mere
lattice work of steel Bolted to the
bottom of the base is casting. circu-
lar, which is really a frame for the
mirror.
Like all great modern telescopes,
Harvard's new giant is a reflector, and
not refractor. The light does not
come through lens and to focus
at an eyepiece through which the OBJ
server looks.
The mirror for the big telescope is
81 inches in diameter. 1t was made
in England many years ago and We
brought to this country as one of two
mirrors supposedly exactly alike. The
other is now mounted in a telescope
in HarvardS South African observa-
torv at Bloemfontein.
The mirror. which has a 10-inch
hole in its center, is made from a
block Of faWleSS glass which cost per-
haps $4,000: to take off a few ounces
of that glass cost the rest OF $4,000,
and perhaps more.
Optics Science Involved.
The mirror is made by patiently
grinding a circular depression into the
iblock of glass. which was, originally II
tinches thick. How it is ground, to
hhat curvature Of the bowl, and why
that curvature, takes you deep into
bptics-
I When it is exactly true-aad proved
Nue by exhaustive tests-it is silvered.
i The starbeam comes down the tube.
ltrikeS the mirror. is reflected and