The morning news. [volume] (Savannah, Ga.) 1887-1900, 1888-09-30

PROF. PROCTOR ON THE WORK
Telescopes ARE DOING

Clden Iime-Great Probleps Still
Remaining for Soiution-Fale Ideas
Too Prevalent as to the Bea Use of
Large Telescopes
Copyright, 1s s, By $. s. Mc01re.
To the lover Ut science, eager . learn all
shat man can learn about tb universe.
not ing can be much more Disappointing
tlal the way in which the DO fers of the
great telescope of the world GEMS to be
wasted. But If this is so to the outsider.
who knows only that telescopeof constantly
increasing power and perfection are being
constructed, which knowledge such as he
can take interest in is not beng correspond
ingly increased, the student of science who
knows how the trouble Is bought ABOUT, is
stil more seriously panied t, find how self
conceit and the desire rather to do what
may seem difficult than to obtain knowledge
which will enlighten the human race, pre-
vent our ablest observers, when put in COM
Inand of tirst-elass OBJ servatories, from doing
what they might to utilize the powers of
the magnificent instruments placed I'm Ter
their control.
If we ask what great telescopes are
wanted for, and what they are actually do
ing, We may learn why II is that their ac-
chievenentS are so disappointing to the non
scientific, and worse than disappointing t.
those who understand the reason of their
failure.
With telescopes Of moderate power GER
tam most interesting and important discov-
cries have been made. And it is certain
that more powerful telescopes can never
make discoveries quite so important in
themselves, any more than the telescope
could disc yer anything quite SO important
and interesting as what the naked eye had
already discovered-as for instance the SUI
and moon, and the five planets, Mercury,
Venus, Mars, Jupiter and Saturn. The
weaker the telescopes first constructed, the
more important the discoveries they
could effect-for the simple reason thai
unless some celestial object, beyond the
range of ordinary vision, we're important
and therefore conspicuous, a weak telescope
would have no chance of discovering it at
all. And pursuing the thoughts thus sug-
Gested we perceive that the greater the zeal
with which the telescopes before construo ed
mad been directed to the study of the
heavens, the less of very striking interest
and Importance remained to be done
by larger telescopes subsequently con-
structed.
Yet it is certain that the world of science
had right to expect from the larger tele-
scopes work WHICH would at least Justify the
expense and labor devoted to their construc-
ton, to say nothing of the salaries paid to OBJ
servers charged with the superintendent of
their employment
The advantages which large telescopes
possess over smaller ones are not always
rightly understood. Everything is suppose
to depend on the size of the glass or mirror
and the length of the tube in which the
glass or mirror is set, the fact being that
although magnitcation and illumination
depend on the telescopes size what is rem
dered actually discernible depends on other
qualities, in such sort that the la gest tele-
scopes the world has yet known have
shown less than some of inferior size but
better optical qualities.
The telescope object glass, really doubls
glass formed of two lenses ia close contact,
one made of crown glass, the other of flint
glass, forms an image OF the object to
which it is directed, at certain distance
called the focal distance} from the glass;
the eye-glass, also double (but the two lenses
are not N contact is in itself a microscope
by which this image is examined. Now
the image thus formed is not pc feet even
if the object glass is perfect, land some of
she 3ject glasses made by the late Alvau
Clarke and his two sons were as nearly per-
feet as could well be-. The image, for
instance of a star, which should be point,
Is disk, with several rings round it. The
details Of the image of the sun or moon or
of planet, are in like degree, though MT
in the same way, affected by optical peculi-
Rrlties. All such peculiarities are magni-
fed by the eye-piece; and although with
magnifying power up to certain value the
defects remain undiscernible; they become
prominent with high powers in such sort
chat there is limit to the power which may
4 IL. AL.
There would be such limit even though
the magnifying effected by the eye-piece
were absolutely perfect But it is not In
this case, as in the formation of the focal
image, optical effects are produced which
modify the details of the object ex-I
amined; and if magnifying power is over
pressed render vision altogether imper-
feet.
To take one of the simplest cases, in order
to recognize the effect of these optical
pecuharlties, suppose we are observing
close double star. The image of this should
be two bright points at certain distance
apart; and the higher the magnifying power
tee more this distance would be increased.
Were the iFna,,,a such as this, all the OBJ
server would have to do in order to recog-
nize the Implicitly Of the star, would be to
magnify sufficiently the focal image so that
his eye could recognize the distance between
the TWO points OF light But as matter OF
fact the image Of the double star consists of
two disks of light, whose false size may
suffice to cover the distance between the
two stars, and prevent the observer from
recognizing it as double, though he may
notice that the image is elongated. In this
case it does not matter how much he may
Increase the magnifying power Of the eye
piece he employs, Tor technically, it does not
matter what power he may use) the two
disks will overlap and the double star Will
remain OFFICIALLY single. But if telescope
with larger object glas is employed, the disks
into which the two stars are OFFICIALLY altered
from their true point-lke character, Tor
the stars are all of them much too tar away
to show their real dlmensions) are relatively
smaller. Ii the object glass is large enough
the stars which had been altered with the
smaller telescope into overlapping disks,
appear as disks separated by well defined
interval. The rings which | before NEIL
toned as surrounding the optical image OF
q star, do not seriously interfere with the
Observers recognition Of the double stars
nature-the distance between its compon-
ents, the direction of the line Joining them,
their relative brightness, and 50 forth. The
larger the telescope the better the view
Obtained. And OF course, in cases where
the study Of double sJarhas been rendered
difficult by the faintness Of one or other or
both OF the componen S, the increase OF SIZE
by increasing the illuminating power OF
the telescope, makes tho ooservaIons Oh
the double at once easier and more satlsLac-
tory.
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