New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1888-09-30
GREAT TELESCOPES.
THEIR WORK DISCUSSED By THE LATE
PROFESSOR PROCTOR
Copyright 1855 BY s. s. Mcclure

,...r 30 sc,e,ce. eager to learn all that man
ran learn about the universe, nothing can oo 'nDo"
moro disappointing than the way III "h'on 'ho ~"
Of the Great telescopes OF the world seem W W
Iut II this is so the outsider, who hho"s o''s "'
.,.sconcs Of constantly increasing power and pcrcc
.2an .re beInr constructed, while knowledge such as
..n take interest in is not being cores pondingy
,n.r.asei the student of science who knows now 'he
trauble is brought about, is stu moro seriously pn"
TO ind how self conceit and the dcsire rahor y. Nv
what may seem difficult than 10 OBTAIN hno"i'ue0
which viii enlichten the human race, prevent our
ablest observers when put In command Oh hrs'o,aSS
observatories from doing what they might 10 u''ne
Tho mowers OF the magnificent instruments placed
under their control h.,
II we ask what great telescopes are wanted ioi'
and what they are actually doing we may learn why
II is that their achievements arc so disapponuns )"
the non-sciennfc, and worse than Disappointing 10
those who understand the reason of their failure
With telescopes OF moderate power certain most In
t.rrstpr and important discoveries have been made.
AM IL IL certain that powerful telescopes can
ncSer make discoveries quite so important In thcm-
selves any more than the telescope could discover
anything quite important and interesting as "hat
fbe naked eve had already dscovereGas for instance
the sun 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 efcct-for the simple reason
that unless celestial object, beyond the range o
ordinary vision, important and therefore con
splcaous a weak telescope would have no chance OF
discovering 1t at ALL And pursuing tho thoughts
thus suggested perceive tna the greater the zeal
ystx which the telescopes before constructed had been
directed TO the study OF the heavens, ha less of very
striking interest and importance remained TO be done
by larger telescopes subsequently constructed
Yet 1t Is certain that the world Of science had right
10 expect from the larger telescopes work which would
4, least Justify the expense and labor devoted TO their
If Tho alarp maid q
observers charged with the superintendence Of their
employment.
The advantages which large telescopes posses, over
smaller ones are not always rightly understood
Everything supposed TO depend on the Size OF the
glass or mirror and the length OF the tubc
in which glass mirror is set. the fact being that
although magnfcation and illumination depend on the
telescopes SIZE what IS rendered actually discernlbe
depends on other qualities in such sort that the
largest telescopes world yet known have shown
less than some of inferior size but better opucal
qualities.
The telescope object-gass, really a double glass
formed of lenses in close contact, one made OF
crown glass the other of fint-gass forms an image
of the object to which it is directed at certain dis
lance called the focal distance from the glass the
eve glass also double (bu the two lenccs are not in
contact IS in Itself microscope by which this image
isscxaniined. Now the image thus formed IS not per
fst even II the object glass is perfect land some %
thea object glasses made by the r'' ia'c
Alvan Clark and lis two sons were As
nearly perfect as could well be- The image, for
instance, Of a star. which should be point
IS disk with several rings around H.
The details of the image of the moon planet
are In like degree though not in the same way affected
by optical peculiarities. All such pecnliartes are
magnifed by the yc-pece and although with mag
nifying powers UP l. certain Nauc
the defects remain undsce mibe, they
become prominent with high powers IN
such sort that there ia a limit to the power which
may be appi,d With advantage to any telescope
There world be such limit c7en though the magn
flying effected by the eye piece were absolutely per
feet But 1t IS not. In this case as In the lorna
ton of the focal image optical effects arc produced
which modify the details of the object examined and
II magnifying power is over pressed render vision
altogether imperfect
To take one of the simplest cases in order TO rec
pgnze the effect of these optical peculiatles, sup
J,bse Ste Fare observing a ciose d6Hble eaE 1aVs
image of this should be two bright points at certain
distance apart: and the higher the magniiying
power the more this distance would be increased.
We're the image, such this, all the observer would
have 10 do in order recognize the duplcity OF the
star would be 10 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 discs OF
light whose false size may suffice to cover the dis
lance between the two stars, and prevent the OBJ
server from recognizing II double, though be may
notice that the image is elongated. In this case 1t
does not matter how much he may increase the mag
nifyng power of the eye piece lie employs Tor tech
nicaly It does not matter what power he may use).
the two discs will stn overlap and the double star
will remain OFFICIALLY single But if tee cope with
larger objccf-gass is employed, the discs into which
the two stars OFFICIALLY altered from their true
pOint-llke character for the stars arc all of them
much too far away 20 show their real dnonsionsl
are relatively smaller II the ohjccts glass is large
enoirA the stars which had been altered WIN tie
smaller telescope into overlapping discs appear as
discs separated by a weldcfned interval Tho rings
which ] before mentioned surrounding the optical
image of star do not seriously interfere with the
observer. recognition Of the double stars naur
the distance between its cCmpODcnt the direction Of
the line joining them, their relative brightness, and
so forth. The larger the telescope the better the
view obtained. And of course, in cases where the
study of double star has been rendered difficult by
the faintness Of one or other or both Of the com
ponens, the increase of size by increasing the num
mating power Of the telescope, makes the observation
of the double az easier and more satisfactory.
What is true of delicate or difficult double star
is true of the delicate details of planet, comet, or
nebua of the moons surface and Of the suns. Every
Increase in the size of telescope, so only that the
opfIcal qualities OF the larger telescopes are good
increases the correctness Of the optical image, and
therefore enables higher powers TO be employed in
examining that image. Moreover, the quantity OF
Light Is increased almost the area of the object
glass mot quite because large glasses must be thicker
and so absorb somewhat light and therefore
magnifyng can be pushed further, for, of course,
nacnifyng Is limited in the case of all objects not,
Ike the sun, intensely bright, by the quantity Of light
In the image The same image which magn.fcd modcr-
ately looks bright and distinct, will, If unduly mag
nifcd appear so dull and dim that It's details Will not
be disccrpible
With large telescopes then, Othcr things being
equal more may be learned about any given object OF
telescope study than with smaller instruments. The
largo telescopes are Of course, difficult to use
efcctually; but that is saying more against them
than II is TO say that hcy cost more n construction
and in repair, or that more must be paid TO the ob
servers who take charge of them. Whatsoever has
been seen in any celestial object with small nstru-
ments, more be with larger ones.
What, then. may We expect from the splendid tclc-