The Washington times., 1894-10-14
FATHER HAGENs GREAT WORK
80 and His Assistants Engaged in the Task
Of Eliminating the Personal Equation
Results Attained OF Vital Importance to
Astronomers al Over the World.

The work referred TO is that done by Father
Hagen and his assistants ID photographing
the stars. with view 10 eliminate the per
sonal equation. The personal equation, -
as it is called, is the difference in the calcula-
tions Of astronomers as TO the time star
crosses the meridian. A young astronomer,
on account OF nervousness, generally sees the
star cross the hair-like mark which repre-
sents the meridian, from one-tenth to three
hfths OF a second before il really does cross.
The older and more cautious astronomer gen
orally makes it about the same time uoo late.
Before this time the time of crossing the me-
ridian was always determined by taking an
average Of the time observed 10y different
astronomers.
About five wears ago. at the centennial Of
the university. it was decided 10 do some
thing TO elevate the tone OF the school and 10
give it a prominent place in the scientific
world With this idea, il was decided to dis
continue the teaching Of astronomy Gt the
university, where it had been taught for half
q century. and 70 devote the time Of the pro-
fessOrs and the instruments at the observatory
to original research. About this time i. II.
PiCeOW the Wall-knOWn astronomer, was
paving a visit 10 the university, and during
his talk with Father FarCis the conversation
turned upon the subject OF photograpnlng
the stars. AIr. Saegmuller, the instrument
maker OF this city. was present, AID plan
was drawn for photo-chronograph.
PHoToGRA APHING A STARS TRANSIT.
This instrument had already been used TO
some extent by different astronomers, but
was subsequently modified and improved by
Father Fargis. The idea is a simple one.
The telescope Is set TO observe the transit Of a
Hrn
plate. The chronOgrapl is set TO beat the
seconds, and whCa the star comes IN view
the observer turns on the switch and at the
same time exposes The plate. The chrOno-
graph has q thin piece OF metal fitted over
the sensitive plate, which, when stIl, keeps
the light OF the star from the plate. At the
beating Of the seconds this metal moves and
exposes the plate for a fraction OF q second,
but long enough for the star to clearly photo
graph itself on the plate. BY this means the
star makes a series Of dots on the plate as 1t
moves across the line OF vision. Marked on
the glass OF the eve piece is 2 halrIke thread
which represents the meridian.
To determine the exact time the star crossed
this line the telescope IS swung around and a
candle held before tie lens. This biackens
the plate and causes the line to stand cut
clearly. BY careful work six stars an hour
can be photographed, although sometimes
the plates do not develop well. and the whole
night S work is lost. Some OF the stars move
so slowly, especially the polar star, that the
plate cannot be exposed every second. For
the purpose Of photoCraphing these stars a
special switch is used which gives the beats
three or four seconds apart, and for the
polar star, hall minute apart. II takes the
polar star four or five minutes TO cross the
field OF vision Of a four inch lens.s The in
strument by which most Of this work Is done
is q transit instrument made by Lrtel &
sity since 1874 The object glass is four and
q half inches in diameter with a focal dis
tance OF about seyenty-eight inches. About
four years ago il was completely renovated
by Mr.. SaegmUler, and is now IN excellent
condition.
The elimination Of the personal equation is
not the only work in the Photographic line
being carried on at the observatory. The de-
termination Of latitudes, and ia particular Of
their periodic variations, by means OF pho
Biography has repeatedly been pronounced
feasible and highly desirable. For several
years the observers at the university have
been working on this line. The first expert
ments were made with floating zenith tele-
scope. or q telescope floating in a bowl Of
mercury. In August, 1891, the order for tho
instrument was given and the objective was
procured from Mr.. Brasbear, and the photo
chronoEraph made by 1Ir. SaeEmuller. The
experiments with this telescope we-e SO sue
cGsslul that il was decided TO make the OBJ
seryatOry permanent station Tor studying
the periodic variations Of the pole.
Atthe instance Of the professors here n sec
ond permanent latitude station was estab-
lisled al Manila. in the PHILIPPINE Islands,
which is also furnished with z loating zenith
telescope and latitude ograph.
E5ther Joseph Algue, S. j.. who was con-
nected with The observatory here, has been
placed in charge Of the Manila observatory.
Since Manila is almost opposite Washington
in longitude. these two stations seem 10 be
well adapted for controlling the periodic va
ratiOns Oftne pole by a uniform method in a
direction almost perpen dicular TO the me-
ridians OF Berlin and Honolulu, where sim
ultaneOus observations are also carried on.
ONE SECOND DOES IT ALL.
Father Algue was not content, however
with the work done by the floating telescope.
so he devised the rejecting zenith telescope,
and assisted by the mathematic theory worked
out by Father J. T. Eendrick. made number
Of interesting and successful observations. In
appearance this instrument is not unlike the
transit instrument but it has two object
glasses. one al each end Of the tube, forming
a double telescope.
The third method Of determining latitude
by means Of photography and the one which
superseded the others. is the utilization Of the
problem engaged the attention of the profes-
sors for some time, and an instrument con-
structed on this plan was made and mounted
by Mr.. Saegmulier. The object-glass is Of six
inches aperture and thirty-ive inches focal
length. Stars of the sixth and seventh mag
nitUdes are readily photographed with the eX-
pOsure Of one second even az the time of the
full moon. 1t is provided with a double
phOUo-chronograph and surrounded with
set OF electric lamps which enable the OBJ
server to readily read the levels.
The next instrument 10 be built is
large transit instrument for Photographic
work. This instrument viii be nine inches
in diameter and the lens as near perfect as
possible. EIr. Claucey, the optician Of Mr..
SRegmuler, is now engaged in making the
lenses. and the instrument viii be ready in
about two years. The professors are now
engaged in preparing the work Of the last
SIX months with the zenith telescope for pub
lication They are also at work with the
twelre-inch equatorial in the dome. which is
fitted with a photo-chronograph This winter
they viii prepare a star atlas OF about 100
stars, and VIII observe stars to the thirteenth
magnitude.
Father Hagen, the director Of the observa-
tory. while very proud OF the results obtained
there. is ayerse TO publicity. He is a highly
educated scientist. having studied at Bonn
and Munich. Father Hedrick who was for
merly connected with the observatory, is now
in charge OF the Cordova Observatory. IN the
Argentine Republic He is well known in
astronomical circles, as be was one OF the
computers for the Naval Observatory and the
Nautical Almanac Tor q number OF years.
Father Hagen is at present assisted by Father
Fargis, who has been devoted 10 the study
and application Of the photo-chronograph.