New-York tribune., 1896-06-21
IMPROVED TELESCOPE.
r,y INCREASED EFFICIENCY HOPED
For
,.osoe c. f. HASTINGS OF NEw-HAvEN
.,.rxs TO REMEDY AN OLD EVIL WHICH
,,s HAMPERED THE PHOTO
GRAPHIC AND srECTEoscOPIc
WORK OF AsTRON-
OAfERS

GRAPHIC AND spECTEOsCOPIC
WORK OF AsTRoN-
49,. ,ope has been excited in the last two or three
' ,hot a somewhat radical improvement in the
''.rcx Of telescopes will be secured in the
en- professor Charles S. Hastings. OF the Shelf
'H'" s.sor,ihc school, New-Haven read a paper be-
ie" National Academy Of Sciences in Washing
wv to in April, and on that occasion gave the
W" ,,h.c intimation OF discovery which prom
p =. WELD the results Just alluded TO. The nature
H x,snt Of TIE reform in question can be better
",,ood BY the average reader II he will first re-
W. .ho one great defect OF the best refractors at
N. present time anu WIZ eo"'uei us 'o''ous pi"0
.i consequences.
% solitary lens. convex on both sides, were used
-, ,,g end Of a telescope. 1t would exhibit two
-, The observer would find Il impossible. by
",r,,v showing the eyepece in and out. TO find
-. =. which all parts OF the image (of the moon
r, oome out with equal Gistinctness The central
=, .,,sr portions would not he in harmony This
~ ~ h. optlcians call spherical alteration" Again
-, a. the prismatc action of the glass. the light
Is hs broken up into the coors OF the rainbow,
>rs canning to a focus a a different point. the
-. osar,st to the lens and the red farthest away
49,. bx placng another lens. of different material
Nv ,.ns behind the first. and calculating their
Zoo. with special reference TO the refractive and
,,.,sjve qualities of the two. an attempt is made
avsrcorne both faults at once. Theoretically this
T. ,oss,ble Practically. /, is not The correction OF
a,.,,,al alteration" is a delicate job. but 1t
made 10 perfection: the correction Of "chromatic
,,.rraon' is never complete Al best. 1t Is only
,-ox,mate In some OF the most famous and most
,,ylv admired telescopes the focus for one end of
-, co,or schedule Is several inches further into the
,,,s at the eve end than the focus for the other
una, the opticians generally aim at, therefore, at
,., in instruments designed chiefly for direc: look
,s ,s TO make the focus for di~tinctness of image
,m. whert the yellow or yellow green rays come
"a point These are the brightest rays of the
gecrum. and are oss' suited lor merely VISUAL
work.
TWO FRUITFUL BRANCHES OF STUDY.
TIE two great departments of astronomical re-
.arch which have yielded the most wonderful. re-
u,s in the last fifteen or twenty years. and which
n. relied upon 10 afford the most interesting reve-
haons in the future. are Photographic and spec
pscopic Mere observation Is fascinating; math-
na,,rs REQUIRE rare talents and sometimes lead to
interesting conclusions: and both are fruitful. They
Md however. subordinate position In stellar
study The camera has not only detected stars and
,sbuae whose existence had not been suspected, but
nhas also revealed unsuspectcd ard startling rela-
tons between these two classes of bodies and thus
has thrown new light Ca the construction Of the
universe The spectrOscOpe has enabled astronO
ners TO guess the materials out OF which the fur
therrnost star is made. discover the motions of
stars toward away from the earth, 10 compute
the period required for the rotation OF the sun
rs axis 10 learn that bodies supposed 10 he single
we're really double to form intelligent surmises re-
gariing the cause Of the appearance Of temporary
s.ars and concerning the possibility Of the planet
Mars being inhabited. and in a host OF ways has o.
!erei US information and suggestion about other
worlds than But camera and speciroscope are
both used at the small end OF telescope. for the
registration and analysis of pictures formed by the
big end. And their service has been greatly ham
Iered by that always remaining and seemingly in
corrigble "chromatic alteration" Of the object
glass
Suppose, for instance. that an astronomer had
telescope designed primarily for purely visual work
but that he wished to PHOTOGRAPH some beautiful
surspot group star cluster. If he adjusted his
snsitive plate the point where the image falling
It vas most clearly Defined and then made the
sposure he would either get no picture a, all
sse badly blurred one. He would find II necessary
% put the plate in the visual focus. but In the
aenca or actfnc focus: and this is at the point
vhere the violet rays come together. The latter
rud be found only by guess or experiment. The
sironomer could not. by actual scrutiny. set the
Instrument ar:gat. Several plans have been adopted
for getting around the d:fculty. In many observa-
tons a special and separate telescope is employed
'.:ted in such way that the visual focus comes In
he violet end OF the spectrum. But an image de-
fined only In blue IS easily seen, as VIII
readily understand when he compares. In thought.
re "non-luminous" flame of an alcohol lamp with
ae dazzling radiance of a gas burner. and fmag-
hes them displayed against dead black back
round. A photogra phic telescope. therefore.
Tot be used for observation. Sometimes third
lsns is temporarily attached the big end OF The
IN he These
cher expedents for dealing with the difficulty,
tough. are costly and awkward
DIFFICULTY WITH THE SPECTROSCOPE.
A similar embarrassment is encountered when
psciroscope instead OF camera is attached to
ordinary telescope. What the investigator would
Ike 10 get. under such circumstances. IS a rainbow
strip Of even width and revealing the black cross
Ines at the red end with exactly the same degree Of
distinctness those at the violet end The band
Which he actually gees. however. Is exceedingly mar
Tow at some point in the yellow for instance.
and broadens out Ike trumpet or a fan on each
side. The lines in the yellow. then. would be dis
unct. though very short but lines out In the violet
red ends would be much longer. but so faint as
% De practically invisible. The spectroscopist has
frequent occasion to estimate the relative intens-
aes OF lines. How he make comparisons under
such circumstances? And how can he hope to get
photographic record OF spectra which will be any
''s nilsiactory? When the extra lens for photo
sspac purposes is brought into place one OF the
'' famous refractors Of the present day the
. IN Nnsth according to Professor Keeler) is nine
'eS 'han usual man would have 10 climb up
~ Instance in the tube. therefore. and even then
N paced at disadvantage otherwise If he wished
an 80 ~ "Ofk with spectrOscOpe. one can see In
Instant therefore, some Of the beauties OF
fsc.InPe whose caromatic Sberra tion IS per-
d.sn; overcome that the focus giving the sharpcst
aruons In purely visual work would also exhibit
ana n3Fs.uum OF uniform width. report the intensity
fsc. oseadth Of each line accurately. and yield per-
ssIss autographs Professor Hastings permits him
,ss, " nope for just such contamination in the
rvoViously. II his dream is realized a telescope OF
Tnew type will be adapted a much wider range
"OTk than IL In ho olii