Evening star. [volume] (Washington, D.C.) 1854-1972, 1929-04-17
ASTRONOMERSFAC ACE
-FOUR BUSY YEARS
WATCHING ECLIPSE
City viii Be on Edge of Total
0bscurity of Sun
in 1882.
LOCATION NEAR BOSTON
CHOICE FOR OBSERVATION
Moon Plays Havoc With Calcula-
tions by Being Off Six
Seconds at Times.
BY THOMAS r. HENRY.

BY THOMAS r. HENRY.
Astronomers have four busy years be-
fore them, according to calculations OF
coming celestial events made at the
Naval Observatory.
The principal event will be a total
eclipse of the sun on the morning OF
August 81, 1882, with Washington IN
the fringe of its path. This will bring
to the United States the International
Astronomical Union, which will lnclude
in its delegations most of the foremost
European astronomers.
The exact path and, route of the
eclipse has been calculated four years
ahead by Prof. James Robertson of the
Naval Almanac Office. 1t will start as
a partial eclipse over British Columbia
early in the morning and sweep east
ward. The sun will be totally eclipsed
from 1927 to 8:24 am, and just north
of Boston there will be totality OF
five minutes and three seconds, probably
affording the finest opportunity for OBJ
servation modern astronomy has known
His four-year forecast, Prof. Robert
son admits, may be off fraction OF
second, since absolute accuracy is de-
pendent on the behavior of the most I'M
practicable of all heavenly bodies--the
moon. The eclipse is due to the moon
getting between the earth and the sum-
The moon never has been known to keep
her dates with the sun exactly on time.
This is one of the mysteries of the skies
which Naval Observatory astronomers
are trying to solve. .
Check Time of Moon.
At present a new catalogue is being
made of the zodiacal stars to get more
exact check on the movement of the
moon. These are the stars, about $4,000
in number, which lie within eight de-
grees on each side of the ecliptic or
annual path of the earth around the
sun. The moon also lies in this zodiac.
BY securing exact positions of these
stars more exact positions can be CAL
culated for the moon when 1t hides
any of them by coming between them
and the earth.
Calculations of The moon are out at
the most about six seconds and all sorts
of theories are being advanced to ex-
plain this. 1t does not, according to
Prof. Asaph Hall of the Naval Observa-
tory, fulfill exactly the inverse square
ratio equation of Sir Isaac Newton by
which the movements of all celestial
bodies are calculated, and some have
pointed out that this condition could be
met by adding one minute factor, which
would be practically the same as apply
ing the Einstein theory.
During the present year, according to
Prof. Robertson'S calculations. there
will be two eclipses of the sun. A Naval
Observatory expedition will study the
first of these on May from one of the
smaller islands in the Philippine group.
1t will be total over Sumatra, where
European astronomers and representa-
fir,1c nf Ax%1a Y,y,ixy
are now gathering. The second will be
a partial eclipse over South Africa.
Two Eclipses in 1880.
Next year there will be two eclipses
of the sun and two of the moon. Only
one of theses partial lunar eclipse
on April Is, will be visible over Wash /!
ington. There will be a total eclipse of |
the sun on April % which will start |
as an annular eclipse over the Pacific |
Ocean, achieve totality over parts of
Canada, and pass northeast over Hud- |
son Bay and lose itself over the Atlantic. |
Another total eclipse will start over |
New Guiana and proceed eastward |
across the Pacific with the sun finally |
shaking off the moon over Patagonia. |
This eclipse will cross the International |
Date Line, so that it will occupy part of |
two days October 81 and %. There will |
be two minutes of totality but the Naval |
Observatory staff has been unable to |
locate a single island in its path appro- |
pirate for an observation post. The |
fourth eclipse will be a partial one of |
the moon on October Z.
There will be five eclipses in 1881. /
The first will be total lunar eclipse !
April 2, passing over the center of India |
and the Gulf of Hindustan. Northeast |
Awe mil ha ivaEf f,fr,
of this eclipse. The second will be a /
partial eclipse of the sun on April 10, |
passing over the Pacific Ocean in the |
Northern Hemisphere. Another partial |
solar eclipse will occur from to pm. |
on September IL, starting over Alaska
and proceeding across Northern Japan /
and disappearing in Siberia. A total |
lunar eclipse is calculated by Prof. Rob-
ertson for September Is, 1881, visible
over the great part of Australia, Europe |
and Africa and touching Eastern South ,
America. The fifth will be partial |
eclipse of the sun on october IL, visible |
over the Indian Ocean.
Eclipse Inaccessible.
On September IA, shortly after the
total eclipse partially visible in Wash /
ington four years hence, the moon again /
will come between the sun and the |
earth over Patagonia and the Antarctic |
Ocean. Due to the inaccessibility of |
the territory to be covered, the eclipse |
will be practically worthless for obser-
walton purposes.
Besides the busy eclipse program |
Naval Observatory astronomers are |
awaiting the forthcoming occultation of |
Eros, tiny planet with a very eccen- |
trio orbit, which at times approaches |
the earth to approximately 100000 (.
miles. the nearest celestial body with |
the exception of the moon. Accurate |
observations of this tiny star are of ex-
treme Importance, because they. afford
a measuring stick for the whole uni
verse. Because of its near approach
Eros cap ra accurately triangulated
with the earth as a base and the star
in the apex of the triangle. The angles
are large enough so that very accurate
estimates Of the distance can be Sc
cured.
Once the distance from the earth of
one heavenly body is obtained, Prof. |
Hall explains, the distance of thesother
planets can be calculated by Keppler's
law.