Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1891-06-28
"A PICTURE OF THE SKY
To Be Taken Through the Tubes Of
the Astronomers Of the World.
SIX YEARS WILL BE REQUIRED,
But With Perfect Arrangements Thirteen
Minutes Would Suffice.
SUNS THAT SHONE ERE THE EARTH WAS
CORRESPONDENCE OF TIL

PARIS, June 18.-The international Pho
tographic Congress, organized several years
ago by group of astronomers, for the pur-
pose of applying photography to the study
of the stars, met recently for the third time
at the Paris Observatory and agreed upon
the latest arrangements for photographing
the heavens
The'idea of applying photography to the
curious things in the sky came to light on
the very day when the great discovery Of
Niepce and Daguerre was publicly an
nounced in the memorable account which
Arago gave of it at the session of the
Academy of Science, April 10, 1889. The
illustrious astronomer perceiving at once
the many and diverse uses to which the dis
covery could be put in astronomical research,
pointed out among other things the possi-
bility of obtaining good map of the moon,
and perfect representation of the solar
spectrum. But the methods of photography
at that day were too crude to admit of secur-
ing satisfactory results.
Early Attempts at Sky Photography.
However, about the year 1845 Sizean and
Flacault contrived to make an excellent
photograph of the sun in 1.6 seconds, very
fine engraving of which may be found in
Arago's complete works In 1849 William
@. Bond, an American astronomer, obtained
a good daguerrean proof of the moon. The
eclipse of the sun on July %, 1851, was
photographed by Berkawski, at Koenigs-
berg, upon daguerrean plate, which dis
closed for the first time traces of the corona
that envelops the star of the day, and the
eruptions that emanate from its surface.
In 1857 Bond obtained very clear photo
graph of the double star Mizar and Zita in
the Great Bear, as exact in truth as the mi
crometric measures, for have been able
to insert it as document in my catalogue
of double stars. 1t was at the Harvard col
lege observatory that these first photographs
of stars were made, and it is there to-day
that Prof Pickering obtains such marvellous
results that in themselves they appear to
equal all those of the 20 or 30 astronomers
composing the European congress M. War
rem de La Rue, in England, and NJ Ruther-
furd, in the United States of America, OBJ
tanned magnificent photographs of the moon
between 1867 and 1867 that have not yet
been surpassed
Making the Moon Look Globular.
Let usnote among these photographs some
startling stereoscopic views that show the
lunar globe so much in relief that it has al
most the form of an egg. This effect, some
what exaggerated, is due to the advantage
taken of a certain movement of Hbration in
order to penetrate, more or less satisfae-
torily, the invisible hemisphere of the moon.
Warren de la Rue, to whom we are indebted
for these stereoscopic photographs of our
satellite, succeeded equally in obtaining
views of the planet Jupiter with an exposure
of 26 minutes
NJ. Flaye, In France, has been one of the
most ardent advocates of astronomical pho
Biography. 1t was applied with the greatest
success in observing the transit of Venus in
1874, and again in 1882. In 1877 NJ. Vans
sen, at the observatory of Mendan, obtained
admirable photographs of the solar surface,
upon which the observer seems to assist, so
to speak, in the phenomena of the forma-
tion of light. These photographs of the
sun are almost instantaneous, for they are
taken in half one-thousandth Of a second.
In 1884 Messrs. Paul and Prosper Henry,
while making maps of the stars for the atlas
of the Paris Observatory, set themselves to
photography for direct observa-
tion, which, at the time, was much more ex-
peditious and certain. At the same time,
and afterward, Messrs. Pickering in the
United States, Gould in the Argentine Re-
public. Gill at the Cape of Good Hope,
Common and Roberts in England, devoted
with the best success, to the
practice of celestial photography Thus
gradually, insensibly, photography came to
take large part in astronomical research. "a,
Photographing the Entire Sky.
1t is now proposed actually to photograph
The entire heavens, and it was with this end
in view that astronomers organized the in
L
then in 1889, and again last April. IN its
recent session the congress paid attention
very largely to technical details. Owing to
political events in Chile and troubles in
which some other States are involved, il
will not be possible for all to begin work at
exactly the same time.
Among other things the congress was con-
,erned with the choice of guide-stars, that is
% say, those which must constantly be held
It the same point of view in order that every
tar may be represented upon the map by a
point and not by measurable space. But
What limit should be placed upon the dis
ance of the guide-star from the center Of
he plate? After much cropping about the
congress decided to leave to each observer
certain latitude not to exceed 40 minutes,
questions of this nature, though secondary,
we're novel and delicate, and q certain lib
rty of action was therefore left to each
'bserver, the congress simply determining
ne end to be attained. The congress adj
ourned after having made the best arrange
nents that the present state of astronomio
allows, for a work of gigantic
and immense difficulty. We
nav look forward with no little confidence
o the success of this undertaking which,
ceording to the latest information, will be-
in in various parts of the world simultane-
usly during the summer
Previous Attempts in This Line.
The matter in hand involves the photo
raphing of the entire heavens and the con-
.ruction from the results of complete
lap which will show the starry firmament
lst as it appears to the inhabitants of the
arth; and this by photography alone by
-hich errors of observation will be wholly
minated. We already have q map Of
his kind, but it Is relatively imperfect and
For example, Argelander,
l 1862, made map of the Northern Hemis-
here, showing all the stars up to the ninth
Iagnitude inclusive, and this map registers
"a, 1913 stars, all of which can be seen on the
lme sheet. Skaenfeld's catalogue of the
outhern Hemisphere gives the positions Of
'S, ,699 stars. NJ. Gould, Director of the
bservatory at Cordoba, Argentina, pub
shed an atlas of the Southern Hemisphere
,me years ago, but it registers those stars
My that are visible to the naked eye.
These efforts represent much patient labor,
ut they can never hope to give what may
G expected from unaided ph0togrsphy.-In