The record-union. [volume] (Sacramento, Calif.) 1891-1903, 1896-04-14
BOUND FOR JAPAN.
Lick Observatory Expedition to Observe
the Eclipse.
Colonel c. F. Croker Will Pay the
Expenses, and Interesting Re
suits Are Looked For.

Dr. Edward S. Holden of the Lick OBJ
servatory furnishes the following 10 the
Scientific American:
1t is proposed to send an expedition
from the Lick Observatory to observe
the total solar eclipse of August next in
Japan. The necessary expenses or the
expedition will be met from a fund pro-
vided by Colonel c. F. Croker, one Of
the Regents of the University of Cali
fornia and a member of the standing
committee on the Lick Observatory.
The expedition will be under the
charge of Professor Schaeberle.
It's programme will be wholly photo
graphic in character Professor Schae-
berle will make large scale photographs
Of the corona with a lens of ~ feet focus
giving an image of the sun about
4-10 inches in diameter on a plate 1Sx2O
inches) on the plan so successfully car
r;ed out by him at the Chile eclipse of
April, 1893
All difficulties in the mounting of SO
long focused a lens are avoided by
keeping the lens stationary and making
the carriage for the sensitive plates
movable. The lens is placed in the
proper position for seeing the sun dur
ing totality. A large canvas tube (4O
feet long, is stretched over a frame of
gas pipe tubing. At the further end of
this frame is an inclined railway carry
ing a holder for the negative plates
QSx20O. A clockwork drives the frame
at the proper speed. The observer is
stationed inside of his telescope, and
makes the exposures according to a pro-
gramme laid beforehand. Some of the
exposures will be very short, in order to
obtain the finer details (only) close to
the suns edge. Others will be longer to
obtain details further out, and these
plates will sacrifice some of the details
close to the edge, for these regions will
be overexposed.
A study Of all the plates obtained in
this fashion will give complete ac-
count of the whole corona, though no
single plate will do so.
Charles Burckhalter, director of the
Chabot Observatory, in Oakland, some
time ago imagined a plan for giving
the correct exposure for each part of
every plate at an eclipse. He will ac-
company the Lick Observatory expe-
dition to Japan and will make a trial
of this plan, using a telescope of four
inches in aperture and of fifteen feet
focus, specially made for the eclipse at
the cost of Hon. w. NJ. Pierson of San
Francisco. (The image of the moon is
about one and seven-tenths inches in
diameter)
This telescope will bemounted equato-
rally and will follow the sun. The
image of the eclipsed sun will fall on
the negative plate, in front of which is
a rapidly rotating diaphra GIN. (The
plate has a hole in its center through
which passes an axis driven by clock
work. On the end of the axis in front
of the plate, and close to it, is rotat-
ing fan or diaphragm.) The diaphragm
is cut into the shape of a double cam,
one cam being inverted, SO that it is
perfectly in balance, and it makes about
five revolutions per second.
One of the double cams has such an
outline that if the corona at the moons
edge has an exposure Of one second,
the exposures elsewhere will be: AT 20
minutes from the edge, 4 seconds; at As
minutes, 8 seconds; at 66 minutes, IA
seconds; at SO minutes, 20 seconds; at
10S minutes, "A seconds.
Other differently shaped cams are
provided, each ready for operation,
with its clock in its special plate
holder. When the plate holder is lifted
the clock starts automatically and runs
for about fifteen minutes. Five or six
such plates will be exposed during to-
tally. Each plate will be exposed much
longer at the outer limits of the corona
(where the light is weakesD than at
the inner limit ewhere the light is
strongesD. 1t is therefore hoped to Sc
cure in this way photograph of the
corona on a single plate, every part of
which has received the proper expos
ure. This single plate will then exhibit
all the details of the corona, and it will
no longer be necessary to build up, as
1t were, the real corona from a series of
plates leach one of which is under
exposed for one region, over-exposed
for another and correctly timed for
another).
Mr.. Burckhalter's ingenious plan de-
serves a trial The only difficulties in
the way are mechanical ones, and these
are now supposed to be conquered.
Besides the 40 foot lens Professor
Schaeberle will take with him 5-inch
Photographic refractor presented to the
Lick Observatory by Miss Floyd and
a Dallmeyer portrait lens of inches
aperture dent by Hon. w. NJ. Pierson).
The former instrument will be used to
make small scale photographs Con 5xI
plates) of the corona and surrounding
stars land possibly comets); and at
least two of these plates will be i'm
pressed with squares of Is, Is, As. SIS,
los, exposure from a standard lamp
before they. are exposed to the light Of
the corona When they are developed,
the squares of standard intensity will
appear at the same time with the image