The dispatch-news. [volume] (Lexington, S.C.) 1919-2001, 1921-10-26

scala. Or. Robert Williams Wood OF
Johns Hopkins had built practical
concave.mirro telescope on Long
Island Ey rotating Il basin of mercury
until the liquid metal shaped itself into
the proper cOncavit% There are
limits to its use, however, according
to astronomers, if the attempt is
made to build the abandoned mine TEL
escope.
The greatest telescopes now in use
sometimes achieve Il power of 1900
times as great as that of the unalded
vision. This is only when the state
of the atmosphere is at its best. Or
dinarily astronomers have to be con-
tent with much less sometimes with
q magnifcation Of POO or 300.
1.-THE atmosphere fixes an outside
limit of magnifcation," said DIR. Frank
Schlessinger, director of the Yale OBJ
servatory. "Limitless magnifying
powers could not be used. Telescopes
will probably be made larger than at
present for use on mountain tops and
especially favorable locations, but the
tendency is to lose in distinctness as
magnifying power increases. Event
ually the object gazed Oh becomes q
blur, as if seen through heat haze.
Only through great instruments like
that at Mount Wilson, and then only
under most favorable conditions have
objects magnifed as much as 5000
times been seen with an unblurred
vision.
If Mars Were Mile Away.
The mine. telescope, if it met the
sanguine expectation Of it projec-
tor, would magnify 25,000000 times,
which would bring Mars optically with
in q mile and half Of the earth. At
first thought this would seem to give
the astronomers sight Of Mars equiv
alent to that which an air pilot OBJ
tains of the earth. as he flies mile
and half above it. At that height
an airman could see cities, towns and
individual buildings, farms, orchards
and thousand marks of the activity
of man. : Under the same advantages
an astronomer would soon know all
about Mars, where the creations Of in
telligent beings are believed to ex-
1st on a much grander scale than on
earth.
But here a difficulty arises. The
airman is unconscious Of the reta-
ton Of the earth, because gravity pulls
the earth and air and the airplane
with a uniform motion. On the other
hand, if Mars were brought within a
mile and a half Of the earth it &ould
be whirling so rapidly that the fea-
lures Of the landscape would be lost
to the eye, as are markings on the
propellers of an airplane revolving ut
full speed.
If magnifcation Of 25,0O0OW
times or anything like it could be ac-
complished the observer could only see
a small patch of Mars. Mars rotates
its 12,OO0-mile circumference once in
q little more than "a hours, so that
at its equator it is making a speed
of about ten miles a minute, or about
five times the speed Of racing car.
If the observers were content with see
ing Mars Is miles off, the portion Wis
ible to them would still be streaming
past the telescope at the rate Of
mile a minute.
A camera Of instantaneous action
might take pictures at this speed on
earth, but it could not be- made on
Mars. A magniication Of 25.00O0OO
times would mean that the light OF
Mars would be diluted to one twenty
five-millionth part Of its brightness i'll
the sky, which would not be adequate
for rapid-fre photography or even for
ordinary vision.