Sacramento daily record-union. [volume] (Sacramento [Calif.]) 1875-1891, 1882-08-25

The GREAT TELESCOPE AT PRINCETON. =
The new telescope for the Halsted Obsery-
atory, at Princeton, has been mounted
within the past few weeks, and is now
ready for work. In magnitude it ranks at
present as fourth among the great refracs-
ing telescopes OF the world, and second in
the United States. lis only superiors in
size are the Vienna refractor, of twenty
seven inches diameter the telescope Of the
Naval observatory at Washington, twenty
six inches in diameter, and the telescope of
Mr.. Newhall, at Newcastle, in England,
which has an aperture of twenty five
inches. A number of still larger instru-
ments are indeed under construction, but
it will be some time before any of them are
actually in place. The object glass of the
PRINCETON telescope is twenty.three inches
in diameter, and has a focal length of thirty
feet. The glass disks were cast by Fell, in
Paris, but the telescope was made by Alvan
Clark & Sons, of Cambridge. Though the
telescope is a little smaller than the Wash
ington equatorial, its mounting ia consid-
erably heavier and frmer, and is i'm.
proved in many respects. The regu-
lator OF the driving. clock is unusually
powerful, and, to prevent friction and
wear of its pivots, its shaft is hoated Ia
mercury. The clamps and slow. motions
are all managed without removing the eye
from the eye-piece, and the declination cir
Gle lie also read from the eye-end by new
and ingenious arrangement of the makers
The object-glass is peculiar in having its
two lenses separated by a space of about
seven inches, so as to allow free circula-
ton of all between them, thus greatly
diminishing the disturbing effect Of changes
of temperature. This construction secures
also freedom from the "ghosts" formed
by reflection between the lenses), which
are so troublesome in many large instru.
ments. The curves of the lenses are not
those usually employed, but are somewhat
like those of the Gaussian system, though
not so deep. The color and spherical
alteration are very perfectly corrected, and
the performance of the glass, so far as can
be judged from few nights work, is
extremely fine. The instrument is, of
course, provided with all the usual microme-
tiers, eye-pieces, and other accessories, but
as its chief occupation, for the present
at least, is to be IL the line of stellar spec
troscopy, special attention has been given
to the spectroscope, which is the most
powerful ever made for star work. 1t is a
direct vision instrument, ON the plan of
that used for some years back at Green
witch, though much larger. L was con.
structed by Hlger, Of London, under the
kind supervision of MIR. Christie (the pres-
ent Astronomer Royal, in accordance with
his own designs. It has three of his So
called half-prisms, Of such size as to take
beam two and one. quarter inches in dia-
meter, and Is neark' six feet long. The
whole cost of the telescope and spectre
scope was S26 600, which was provided by
the generosity OF Robert Bonner, r. =.
Stuart and other friends Of science and the
college. The observ atory itself, of which
the corner stone was laid sixteen years ago,
has been newly fittstl up for it's occupant.
a gas engine furnishes the power for NOV
ing the dome and working the shutters,
aud it also drives az Edison dynamo cleo.
trio machine which provides powerful
current to be used ;or lighting purposes,
or to supply the spectra of gases amp
metals TO be compared with the spectrs< Of
the stars