Harrisburg telegraph. [volume] (Harrisburg, Pa.) 1879-1948, 1919-05-30
Will "Snap" Eclipse
From an Aeroplane
BY GARRETT P. sERvIss

one of the most interesting as
Economical experiments that have
been tried in a long time will be
Prof. David Todd's attempt to pho
tograph the total eclipse of the sun
May 30 from u naval aeroplane sent
up to an elevation of 10000 or 49,
600 feet from a ship in the middle
of the Atlantic ocean, between Africa
and South America.
If it succeeds the result may be
great advance in our knowledge
of what is, perhaps, the most mys-
terious phenomenon in the solar
system - the corona of the sun -
which is believed to serve as an in
dex of the suns electromagnetic con-
troll over the earth.
This wonderful phenomenon,
which always arouses a profound
sentiment of awe in every beholder,
appears in the form OF vast
glory" composed of a glowing
crown closely surrounding the placK
orb of the moon as it covers the SUM-
and great rays and streamers, otten
of strange shapes, extending OUT
ward from the crown to distances of
millions of miles.
The corona varies both in general
shane and in details, as seen during
successive eclipses, and these Varia-
tions are believed to accord in some
manner with the character and IN
tensity of the solar activity, whlcn
are also indicated by the existence
and motions of apparently piack
spots on the suns surface.
It has been proved that magnetlc
storms on the earth are somehow
connected with these mysterious
happenings on the sun. The connec-
tion is sometimes startlingly pro-
claimed by the waving in our at
mosphere of immense curtains Oh
lambent electric fire. called the au-
rora borealis. which is not ihile
uuently accompanied by violent
sparks leaping from telegraphlc III
struments. ~, ,,ore
Unfortunately. owing to the glare
produced by sunlight in the alilloe-
phere, the corona cannot DC ~
except when the OPAQUE oooy ol S,, C"e
moon intervenes to shut out, ike
black screen, the disk of the sun,
whereupon the strange glory
hursts into view. Usually the totai
observation by the moon lasts put
one or two minutes, but on TINS oc-
casion it will last more than slA
minutes and half. o,v
A total solar eclipse has rarely
been seen from great attitude pe-
cause the path of such an ecilpse is
narrow and seldom happens to run
over a. mountain peak attalnaple py
astronomers with their instruments. @
FOR this reason Professor TODD
ohservation, if successful, VIII pe
UNIQUE. At a height of ABOUT tWo
miles nearly all the Clouds "hlcn
often spoil eclipse observations from
lower levels, will be surmouhteu,
and in addition to that the observe.
with his Photographic instrument
,,,iiI he above that part If the atmos-
phere which is most effective IN cut
tinq off the actinic rays of lght
which are the ones that aftect tne
nbotoeraphic plate. Thus there is
reason to hope that the photographs
obtained will be much better anu
nerhaps incomparably better, thah
any hitherto taken.
one great difficulty in the way OF
astronomical observation presenter
nv a ship at sea may be aVoldeo pS
the use of an aeroplane. owing 10
the constant agitation of the ocean
u,rface. even in calm weather, by
the slow heaving and swelling of the
surface of the water, it is impossible
to maintain the pointing or an IN
strument in a fixed direction; but In
the case of a relatively faint pho-
nomenon like the corona 1t is neces-
sary to expose the Photographic
plate for a considerable interval OF
time in order to obtain a good I'M
preston of the light. OF course II
the instrument is swayed by rock
ing motion of it's base it cannot be
kept steadily pointed at its object,
and only a blurred picture will be
obtained.
With an aeroplane, however, this
trouble may be largely, if not en-
tirely eliminated, since the aero
plane does not oscillate like a ship,
but when held on a steady course
plides with remarkable smoothness
through the air and moves on an
even beam.
II il rolled like a ship it would
disconcert the aim, swinging the IN
strument through, perhaps, several
degrees of arc in a second, but IN
calm weather the only motion OF
the aeroplane is in the direction OF
it's flight This motion, as long as 1t
is straightaway, and its inclination
to the horizontal does not vary,
would not affect the pointing of an
instrument toward an object at a
practically infinite distance. 1t
would only be necessary to hold the
aeroplane on a virtually straight
course during the time the photo
graphic exposure was being made.
on the other hand. if the course
were circular the direction of in
clination of the deck" would swing
round all the points of the compass,
unless the circling was performed in
a perfectly horizontal plane. Efforts
to counteract this by means of
gyroscope would probably not prove
practicable.
Professor Todd has been present
at almost every total solar eclipse
in the past forty years, and his at
tempt to see the spectacle this time
from the flies will be watched by
the astronomers of the whole world
with deep interest