The San Francisco call. [volume] (San Francisco [Calif.]) 1895-1913, 1895-10-20
TAKING PHOTOGRAPHS Of OTHER WORLDS,
ny ROSE oHALLoRAN.

ment of facts by the gifted writer of this
historical sketch of photography of the
heavens we discern the very opportune
appearance in the ranks of astronomy of
/ one slngularly adapted to the needs of the
period, when the camera was practically
recognized as an important astronomical
instrument
though omitted in the pages it is a we'll
known TACT that the timely combination OF
PHOTOGRAPHIC and astronomical skill pos
/ seSsed by Professor Barnard led to methods
that were eminently successful. Dealing
chiefly with results, he describes how an
Old portrait lens OF short focal length
revealed the varied density and cloud
/ forms of the milky wav and the black
holes that seem to perforate the mass of
stars, and gave glimpse of the starless
/ depths beyond. This now famous lens,
| SIX inches IN diameter and thirty-one
inches IN focal length, has been recently
mounted and refgured; but the illustra-
ton shows 1t was in the August OF 1889
when the true structure of the milky way
was first disclosed.
he explains how the light of the stars
leaves trail on the plate owing to the
1 rotation Of the earth describing circles If
directed to the pole and straight lines II
! the equatorial stars are in the field OF
tanned by keeping pace with the heavens
moving westward. thus counteracting the
/ effect of the earth S rotation.
! BY this arduous process stellar orbs in
! visible in any but the largest telescopes
! leave their faint record on the photo
! graphic plate. But this wonderful portrait
! lens has also brought to view other things
invisible. Dim nebular outlines and faint
! cometary details never before revealed
| have disclosed their existence; and in
/ October, 1892, a new periodic comet was
detected among the starry myriads on the
plate, when one of his arduous vigils of
several hours came to an end This was
the first comet discovered by means of the
camera.
The marvellous structure and rapid
changes seen i'll Swift's comet and other
recent cometary visitors and which were
unnotlceable in telescope, are dlscov-
| cries that have already created a world
| wide interest. In these interesting pages
attention is also called to the perfection at
tanned in eclipse photography WITHIN the
last few years, especially in January, 1899,
when excellent work was done by many
Californian astronomers, and in December
/ OF the same year, when splendid photo
graphs were obtained by Professors Burn
nam and SChaeberle, and afterWard by
| Schaeberle in 1898 in Chile. But in pictur-
! ing the details OF the sun disk, Jansen OF
/ Meudon attained the best success years
| ago, though many obseryatories, including
/ the Lick, take excellent photographs every
clear day. Quite recently Professor Hale
OF Chicago, by an ingenious device, sur
passed all previous attempts to depict the
solar prominences by means of the spec
/ troscope. Spectroscoplc photography, or
the art of picturing the refracted light of a
heavenly body by means of the sensitive
plate, has also progressed since commenced
more than thirty years ago by Higgins OF
/ England
Slight changes in the lines of star spec
ira have led TO the discovery OF bodies
some too distant to be ever detected by
telescope vision, and others undiscernible
on account of their non-luminosity.
Professors Pickering and Campbell have
made valuable Investigations in this way
Under the direction of Professor Wal.
den fine photographs of the moon in all
its phases have been taken at Mount Ham
ilton. For general outline OF lunar
topography the camera gives the best re-
suits, but for fine detail even a small tele-
scope is superior.
This enthusiastic observer then describes
wildly the sublime views given by the
thirty-six Lick telescope of the lunar era
ter depths, when the air is still, and the
high powers can be used.
At such times countless unrecorded de-
tails are to be seen which the photo
graphic plate is helpless to depict until its
capacity receives some extraordinary ad-
vance. Planetary detail is also nearly be-
yond the reach of the camera, the best
representation OF Mars during the propi-
tious time of its near approach to the
earth being merely drawings from visual
observation. Furthermore, this earnest
astronomer regrets thatno valuable results
were obtained, and states that: Until the
difficulty OF photOgraphing 4 directly en-
larged image in the telescope is overcome
and it certainly should be-nothing can
be expected from photographs of Mars.
When this is done many revelations will
come to light concerning the physical con-
ditions OF that planet"
These few paragraphs merely allude to
the most striking points of this valuable
article on the history OF celestial photog-
raphy. 1t is profusely illustrated by sky
pictures of rare merit.
ROSE O'HALLoRAN.