The Providence news. (Providence [R.I.]) 1891-1906, 1896-06-24
A GREAT TELESCOPE.
II Is the Largest Photographic in
strument Ever Made.
An American Woman Gives II, and Amer
lean Workmen Make IL

professor John A. Brashcar, tho famous
astronomical instrument maker Of Ale
ghany, will begin soon the manufacture OF
tho largest double Photographic telescope
ever made In the world. 1t Is being made
for DIR. Max Wolf, tho eminent German as
tronomer Of Heidelberg university, aud
has the remarkable distinction Of being
the first instrument of its kind ever made
outside of Germany for Germany.
The great instrument was the gift Of
Miss Catherine Lorillard Bruce, who pre-
sentcd tho Harvard astronomical observa-
tory with large telescope to be devoted
exclusively TO photographic work, and the
gift was made after DR. Wolf had made
many vain attempts In Germany 20 secure
money for the instrument. He has made
many discoveries with smaller instruments
and very meager means, and he was al
most discouraged In his ambition to secure
, larger telescope when an American
woman came to his rescue.
DR. Wolf had visited Professor Brashear's
workshop In Allegheny In 1903, and after
studying the work there carefully he ex-
planned his desire and ambition. AS soon
| as he received the gift DR.. Wolf wrote to
Mr.. Brashear, and tho latter worked ont
the designs. The curves Of the lens have
already been sent TO the optical glass fac-
tory at Jena, AID glass disks are now being
made
There will be eight lenses, each 16 inch
es IN diameter, and these will weigh when
finished, without mount.ngs, about 400
pounds. The instrument will be 1914 inch
es In diameter, with clear aperture Of ID
inches and tho extraordinary short focal
length Of 1870 inches. This will give large
Photographic field, taking in an area of
the sky about 90 times the diameter of the
full moon at the same time concentrating
such q great amount of light on the pho
tographic plato that the faintcst stars,
planetoids, nebula and comets will in
very brief period impress their images on
the plate
Great difficulty has been encountered In
making disks for these lengths on account
of the great thickness of glass and very
deep curves. IL Is expected the disks will DO
in the workshop before summer is over,
and about four months will be required to
finish the instrument. The instrument
at present used by DIR. Wolf equal to the
largest now in the world, has only six
inoh aperture. The new instrument will
be eight times more powerful.
side by side are found In repeating the ex-
posures In order to determine with great
certainty that the object photographed Is
really Many defects on plate
develop themselves where least expected.
The double telescope will reduce the
chances OF error enormously, as il two pho
tographic streaks are found upon both
plates, and In the same relative position
with star or stars, 1t Is almost certain
TO be a planetoid.
Professor Brashear, in speaking last
night OF the .sSs instrument and its prob
able worth to the world In the hands of
DIR. Wolf, said:
"Dr. Wolf, as director Of the Heidelberg
observatory, was the first astronomer to
discover asteroids photographically When
photograph is To be taken Of the stars,
the instrument is held rigidly and accu-
rately upon any one star in the field OF
stars to be taken. No clockwork has ever
been devised that will do this well enough
on account of the difference In the refrac-
ton of the atmosphere at various angles.
The observer constantly watching in Wis
ual telescope TO which the Photographic
telescope Is attached, touches al independ-
ent screw, giving such slight additional
motion as will keep the star accurately
upon one point on the plate.
"Now, as the stars have no motion In re-
lation TO one another that can be detected
In so short a time as Photographic plate
Is exposed, each star viii be found as a
small circular disk on the photographs
plate when it is developed and in It's prop
er relative position. 1t Is not so with the
asteroids These little bodies revolving be-
tween the orbits of Mars and Jupiter will
81
on Photographic plate II such bodies
are moving among the stars that are be-
Ing photographed. They will leave track
or trail instead of circular disk. For an
exposure of about four hours the trail Is
one tenth inch long. AS the trail is usual
ly very faint a second photograph is taken
of the same region, and if the trail is found
to have continued itself in the same track
then IL is quite certain it is an asteroid or
one of the smaller planets.
"Dr Wolf was the first astronomer 10
discover asteroids by this met cd, and In "A
few years he has added abou, 40 Of these
plancto.ds TO our system. He has also re-
discovered by photography number of
others that have been found usually. All
this has been done with very neager
means"
The eight inch double telescope ordered
by the Imperial observatory Of Japan at
Tokyo for Director Tirao Is very nearly
ready and will be shipped about the first Of
next week. This instrument was made es-
pecially by Professor Brashear for photo
graphing the solar corona at the time Of
the eclipse of tho sun which occurs Aug s,
this year. 1t is TO be set up near Yeddo,
which IS in the line OF totality. The Amer
lean Observers from Amherst university
arc already on their way in a private
yacht, and the party from Lick observa-
tory sailed May %.
Professor Brashear Is also making oil
the optical equipment for the Royal OBJ
servatory ut Cape of Good Hopc and six
Inch double Photographic telescope for
Harvard university observatory. - Pitts.
burg Dispatch.
His wondrous Healing Power.
Charles Strong, % young mechanic bf