Evening star. [volume] (Washington, D.C.) 1854-1972, 1897-06-18
THE YERkES TELESCOPE.
The Astronomers Who Will Have
Charge of 1t.

Charge Of 1t.
From the Chicago News.
Mountain peaks have their disadvantages
as well as advantages; and as an important
branch of the work undertaken at Lake
Geneva will relate to the sun, 1t has been
necessary to consider daytime conditions
well nocturnal ones. The belief has
been expressed, moreover. that in the win
ter season there will be more cloudless
lights in southern Wisconsin than on
Mount Hamilton.
The great +Iinch glass is mounted in a
lube sixty-three or sixty-four feet long.
Its focal length bears about the same pro-
portion to its aperture as is the case with
the Lick telescope, which S nineteen to one.
A "dev cap" designed to shelter the object
glass from mist and frost. reaches ont fully
eight feet from the big end of the tube, and
it will often be necessary to attach d
Spectroheliograph' other instrument
ten feet long at the eye end. y tower
ninety-two feet in diameter is none too
large, therefore, to accommodate both ap-
paratus and astronomer. The center of
the tubes motion on its great axis is for
ty-three feet abovethe base, the pier pill
lar on which it stands. and when the tele-
scope is pointed vertically the other end of
the dewcap is eighty feet above the base.
The floor is movable, in order TO accommo
date the astronomer when he changes the
angle of the mighty instrument with the
sweep from east TO west the tube is
tuated with a driving clock. itself weighing
a ton. No Photographic corrector will he
used over the big lens; but arranged on the
outside of the same tube with it is g.
inch lens, whose foo al length is sixty-fsur
feet. This will be used to get direct pho
tCeraphs OF the sun: and for photographing
stellar spectra small corrector Will be put
inside the big tube down near the eye end,
in accordance with a suggestion made some
time ago by Professor keeler. For another
important and unique branch of photo
graphic work which will be carried on at
Lake Geneva still another attachment will
be made, which will presently be explained.
Two important members of the s:aff at
Lake Geneva will be the double star
pert, S. W. Burnham. and E. E. Barnard.
who has won rare distinction by mis- dis
covery of Jupiter's fifth satellite, mis- pho
tographs of Milky Way nebulae. and 9TH
err work. The greater diameter of the
Yerkes glass will enable Mr.. Burnndm to
divide close doubles which could not lie
separated on Mount Hamilton. although
| the average seeing will probably be in
ferior. Mr.. Barnard will give special at
tention to planets. satellites and comets,
ard, in observation of exceedingly faint
and distant objects. will have the benefit
of the superior light-ga thering power of the
40-inch, which is about one-fourth greater
than that of the Lick telescope.
The director of the observatory, George
+. Hale. Is young man, who excited the
admiration Of astronomers five or six years
ago by his SpectroScopic explorations of
the sun. He established in Chicago a pri-
waite observatory of his own, and set up
therein a Pinch glass which has since
been removed to Lake Geneva He then
lIyelted an exceedingly ingenious and orig
inal instrument called the ."spectrohclio-
glaph." This takes a picture Of the sun in
a new way. Instead of letting the solar
image fall directly on the sensitive plate,
Professor Hale analyses the light with a
srectroscope, and then uses only that very
limited part of it which is to be found in
one of the bright cross lines of the solar
spectrum. The particular line which he
usually selects is a broad one, attributed
to incandescent calcium vapor. The ap-
paratus is SO managed that only such por-
items of the suns surface as abound in this
material are registered on the plate. In
the same manner he gets pictures of the
cEromospheric ring and promnences on the
SUMS limb. the disk itself being covered by
a round shield. 1t is impossible to give an
adequate idea mere of the importance Of
this new method of research. But ii
should be added that this work will be car
ried on at Lake Geneva more extensively
than at the Kenwood observatory, and
that Professor Haie's methods have in
splred the confidence OF the leading spec
tro scopists of the world.