The southern aegis, and Harford County intelligencer., 1863-12-25
DECEMBER rs, 1863.
to the company, the ladies' in waiting and
the lady guests acknowledging the obeis-
ance by sinking to the very ground. ~
f,tH4fT - fEVfIF a.
Great Telescope and Photographs Of the
Moon. ~

III The American Journal Of photography
contains very full report Of Henry Ora
per's paper recently read before the Ame-
riean Photographed Society on his new
telescope, andsxtbe, large AAsssapAs
which he has taken of the moon. In the
paper it is stated that in the autumn Of
1858, DR.. Draper determined to make the
largest rejecting telescope in America,
the construction of which with various
Improvements introduced, have occupied
his time up to the present period-more
than five years. This telescope is pearly
16 inches in aperture and l3 feet in focal
length, and was intended to be devoted
to celestial photography; consequently it
has many novelties fitting it for this pur-
pose. 1t has the largest silver reflector Of
any instrument in the world, with the ex-
ception Of one in the Imperial Observato-
ry at Paris. A rejecting telescope is
greatly superior to an achromatic one for
Photographic purposes. DR.. Draper first
used speculum metal for his mirrors, but
abandoned it at Sir John Herscheps sug-
gestion in favor of silvered glass; the re-
feoting power of the latter being 93 per
cent. that of the former being but 75.-
The glass mirror also only weighs 16
pounds, whereas one of the same size of
speculum metal weighs 1873 pounds; and
if the silver of the glass should accidental
ly be injured, it may be dissolved off by
nitric acid and the mirror re-silvered in
the course of few hours. This may be
repeated as indefinite number of times
The mirror of this telescope has cost DIR.
Draper an immense amount of toll, in Or
der to reach as nearly as possible to per-
fection. He ground more than one hum
dred mirroas Of different sizes, from nine
teen to one quarter Of an inch in dame
ter. The mirror of this telescope is sus.
tanned in walnut tube hooped with brass,
and the frame in which it is mounted
holds it at both ends to avoid the tremu-
lous motion 80 common to large instru-
ments. When photographs of the moon
are being taken, the telescope is not driven
by clock work, but is allowed to come to
complete rest the sensitive plate alone
is moved in direction and at rate to
correspond with the moons motion. BY
this mode of operation, only one ounce
instead of half ton is moved. The oh.
servatory of DR.. Draper is situated at
Hastings, N. Y, on hill $50 feet above
the level of the sea. The dome which
covers it is 16 feet in diameter, supported
on point at its centre, and can be turned
with gentle pressure of the hand. The
instrument can be directed to an object,
shifted, and the observer himself moved to
any one part of the building, by a very
slight exertion, "A Photographic labora-
tory is attached to the observatory. 1t
contains all the requisite conveniencos for
taking photographs up to sizes Of three
feet in diameter. One Of three and one
of two feet in diameter.of the Moon have
been taken. The former represents the
moon on scale Of 70 miles to the inch /;
the latter-two feet picture-is the largest
that had previously been made anywhere.
Celestial. photography is as yet only in its
infancy, but it is progressing rapidly.
From The Irish Times