The Wichita daily eagle. [volume] (Wichita, Kan.) 1890-1906, 1902-12-14


may look out in any desired direction.
The Yerkes Observatory's big telescope
is primariaiy for the visual study Of the
heavens. but TO use it for Photographic
I nr,rnoses no camera attachment is requir-
ed. The telescope itself, with its lens
and focal length of sixty feet, acts as
the camera. The telescope is regulated by
clock work so that it viii follow accur-
atelv the apparent course Of the heavenly
bodies across the sky. But TO insure alb
solute accuracy, il is essential that dur
ing the time of the Photographic plates
exposure, an astronomer should be sta
toned at the telescope TO correct by hand
any minor deficiencies in minutely follow
ing the passage of the stars and celestial
objects across the sky:
To regulate so carefully 4 telescope
Weighing seven tons became a problem OF
| great difficulty. Mr.. Ritehey solved the
question by inventing double slide plate
! carrier TO hold the Photographic plate in
which the astronomical Image is to be
imposed. Minute corrections are now
made by governing the movements of the
plate rather than the telescope.
| Another difficulty was that refracting
! instrument constructed for visual pur-
poses has its lens corrected in such
way that the yellow rays of light which
affect the eye most intensely shall be
brought to sharp fo~us. neglecdng the
blue rays. which are most active photo
graphically. a visual telescope is there
fore far from adapted Photographic pur-
poses. inasmuch as the yellow rays 70
cussing at one point in the tube and the
blue rays focusing at another point su-
perimpose two images On the plate to be
exposed.
It was found that a photographic
plate could be made especially sensitive
to yellow rays Of light Mr.. Ritchey then
perfected a yellow color screen which is
placed just before the plate. II lets into
the plate only the clear cut, sharp yell
low image and shuts out the blurred rays
OF light in the photograph with refract-
ing telescope the fainter of the stars and
nebulae an exposure of from three to
FIVE hours is necessary and then only is
possible under the most atmospheric con-
ditions To photograph the moon, how
ever, because OF its brilliance ond eompar-
alive proximity to the earth, an expos
ure of half a second is ali that is re-
quired.
Mr. Ritchey has some very interesting
pictures Of the moons entire surface,
taken on such a big scale that the whole
set Of photographs make 100 foot pho
tograph of the moon. The pictures on
this scale, it is estimated, brings the moon
within sixty miles of the earth.
So much for the work that Mr.
Ritchey has done with the refractor tele-
scope for astronomical photography, but
it IS on the rejecting telescope that Mr..
Ritchey bases much of his hope for fu-
lure revelations of the mysteries beyond
the skies.
For eighteen years Mr.. Ritchey has
been working on a reflector, but it is only
in the last six years that he has been
able to develop his ideas on a large scale,
with remarkable success at the Yerkes
Observatory. In the rejecting telescope
there is no lens used at all There is
simply highly polished silvered glass
mirror, which reflects the image to the
sensitive plate. The chief advantage of
the reflector is that il brings all rays of
light of whatever wave length to the
same focus and there is no question
of blue or yellow images. In the reflector
at Yerkes Observatory the mirror is two
feet in diameter, with focal length
of eight feet. This type of instrument
Mr. Ritchey finds, is the best possible
means for ASTRONOMERS. photography of
faint heavenly bodies. For photograph
ing the brighter celestial objects. such as
the moon, the forty inch refractor is the
better instrument, merely because its TO-
cal length is eight times greater than the
eight foot focal length Of the two foot
reflector
with the finest atmospheric condi-
tons" Mr. Ritchey said to me- photo
graphs taken by the two foot reflector
show that the nebulae are not diffused
hazy masses, but that their structure is
most complicated often consisting of ex-
Quisitely fine filaments and delicate mar
row riffs. In these photographs the in
tersections of such flaments and riffs can
be set in the measuring machine with al
most the same accuracy that is possible
in the case of star images. Changes of
form of the nebulae, if such occur. could
be detected with certainty by such pho
tographs.
There can be no question in regard
TO the superiority of the Photographic
method over the visual one for the de-
lection Of such changes and for the study
OF the nebulae in general -Ae experience
gained in the construction and use OF
this instrument and the results obtained
with it are most interesting to me as
showing the possibilities of the future
great reflector IN astronomical photo
graphy
Mr.. Ritchey went on 20 say that ne is
now constructing ive-foot reflector,
which he hopes TO accomplish stin better
results.
The Professor present astronomical
photographs show stars three and four
times fainter than those at the limit Of
the visual telescope. These pictures with
which he illustrates many of his lectures.
are extremely interesting. Mr. Ritchey
has photographed the great nebula in
Cygnus with an exposure Of three hours.
The faintest stars shown in the original
are more than ten thousand times fainter
thsn the unaided eye can see he has
photograph of star clusters which show
ten thousand stars in plate eight by
ten inches. a picture showing the lunar
crater Ciavius which is l43 miles wide
and 1890 feet deep: pictures Of comets
with tails all on one plate, Of star clus-
terS. with four thousand stars in a single
group. SO closely massed thar their in
dividual outlines cannot be distinguished.
one Of the suns corona. Of vaporaus.
fiery masses Of hydrogen ana calcium.
forty thousand miles high shooting out
from The surface Of the sun and seven