Evening star. [volume] (Washington, D.C.) 1854-1972, 1881-07-03
OBSERVING the COMET.
HOW the Work is Done ut tho Oh.
servat0ry-DefininE Its Position

seHS0tOfy-Dehfufnx HIS POSITION
Automatically.
The unexpected coming OF the comet has de-
| veloped an unusual interest In astronomy. In
old times these visitors were regarded as dread.
| iul emeDs OF evil, but now methodical science
| fnspects them as coldly as a physician would
| view an unusual deformity or q naturalist In
lie The present comet instead Of
| people, has only excited their curiosity. Every
/ one wants TO see 1t, and to learn all the facts
about II. he grumoles II careful and delio srate
scientists are unwilling TO answer his questions
| at once. This curiosity has attracted an unu-
| sual number OF visitors to the OBSERVATORY
| during the past week.
observations are taken OF the comet "a they
are taken OF any other heavenly body. though
there Is an exciting interest In the work which
Ielleves 1t Of any sense OF drudgery. An as
tronomer
ON THE LOOKOUT FOR COMETS
uses generally small glass-one that he can
handle easily and which has broad field. The
comet, having been discovered, the first point
to be determined is its position,-its right as
cension and declination corresponding to the
longitude and latitude, OF point on the face Of
and three observations taken at equi- distant
umeS,-aDOut week apAl 1.-THE astronomer
t ny series Of computations, is enabled to de.
orbit, from. which 1t is an easy matter for
him to compete the size, distance from
tae earsh ana rapidly OF motion OF the comst
ION as to when 1t Will return. These objarVa
ions are taken on
THE TRANSIT CIRCLE"
large glass, which Is mounted, exactly on a
line with the meridian. This glass Is located
In little wing at the west side of the Observ-
atory. There is an opening through the roof
ana in the north and south sides sf the square
structure looking as though some one had II
slice from the middle OF 1t. The glass inside
is mounted. as accurately as science can mount
fc1r frnyv
II never swerves hairs breadth towards the
east or west. star seen through 1t, Is sup
supposed to be exactly over the meridian line.
BY this glass the right ascension and deciina-
In case OF strange body, II Its approx.
mate position In the heavens Is known.
ara that can d3o,l be determined with the
the glass is set so as to cover 1t when
IL crosses. On either side OF the glass are
large wheels, which revolve with the glass.
These wheels are scaled and graduated so
timely that microscopes have TO be used to read
the measurements. PreSuming that the IN
strument has been set right, the observer,
| through the glass. The field of the glass is
crossed up and down with fine lines In several
groups OF two, three and five. There are also
two fine hair lines from right to left.
THE OBSERVER
has in his hand a Geographic key, which con-
| meets with an electric chronograph. When the
comet enters the field Of the glass; as 1t crosses
each line, the observer taps the key. The two
horizontal hair lines are adjustable by means
OF little screw In the eye piece OF the instru-
| ment. and the observer so adjasts them, that
| the center OF the nucleus is exactly between
the lines The comet is not greatly magni-
fed In the glass. but is very clearly de-
fined fined There appears to be black
point where the tail seems to split. When the
comet has passed over the meridian at its lower
elimination. which It does now a little after II
OF nj nhd yNry,,
commences. He has TO note the time on
THE CLOCK
This is no ordinary clock. but one set In q
vault, where 1t is free from all disturbing infiu
ences Of varying temperature, with nothing
but its face showing. 1t keeps sidereal time.
me hour and minute taken from the clock, and
the records made by the chronograph. give
DOWN 10 the tenth part Of a second the time
that the comet crossed the meridian, the CEN
tral line on the field Of the glass representing
me meridian. The time OF the passage is easily
words, to s1dereal longitude Just as the lonoI.
tude OF town can be calculated by Knowing
its tlme me register or scale on the wheel on
tne nortn OF the glass, considered together with
q little register connected with the screw regu-
iatlng the horizontal lines on the field Of the
glass, indicates
THE ZENITH DISTANCE
OF the body observed, which Is readily convert.
able into declination or sidereal latitude. The
TO give correct idea of the accuracy With
which the time can be determined. II consist g
OF revolving cylinder. covered with sheet of
paper, so placed that an iron from an electric
apparatus makes marks at regular intervals
The apparatus is delicately adjusted, so that
the interval Is exactly a second. The tapping
OF the Key held by the observer makes an extra
mark. and any school bog would soon learn to
TELL by means OF these marks, the eX act tima OF
each tap. When the astronomer mas Obtained
Lne right ascension and dechnation in the m m
ner oescrlned ne really has just commenced
Ills Work. He has before him the tedious task OF
CORRECTING ERRORS.
1t Is always presumed that there are errors,
made by the clock and by the instrument or
lass. Though the most delicate appliances of
c1ence are used in mounting aud adjusting
these meridian glasses 1t Is found that they
are SO seldom accurate that astronomers
always take 1T for granted that there are some
errors 10 figures first obtained. A deviation Of
hundredth part Of a hairs breadth could
hardly be detected on the earth, but where the
line OF vision extends millions OF miles into
space. It Is apt to seriously affect nice calculs-
intricate experiments and calculations to cor
rect the errors OF the clock and of the insuru.
ment. The instrument Is tested with fine
built upon the ground and is Independent OF
the Observatory building, Is pool or trough
OF mercury. The observer, In order to satisfy
pend1cularly points directly to the zenith, must
first see the lines on the field reflected back
from the mercury. So sensitive Is the mercury
to all disturbances that II wagon is passing
near the building the surface Is 80 disturbed
That no reflection can be seen at all when look
Ing through the glass. The observer, having
corrected the errors by long and tedious COM
putafions, finally obtains correct statement
OF the position OF the comet. After taking
three such observations. week or more apart,
he Is ready to compute the elements OF the
comets orbit.
AN ASTRONOMERS LIFE.
at is popular idea, , said Mr.. Winlock, the
astronomer who explained the method OF TAX
ing observations to a STAR reporter "that an
astronomers life is poetfcal one-that all he
has to do Is to contemplate-gaze through
glass and think. There Is considerable drudg-
cry and sameness about observing"
"Can the computations so far made about the
comet be correct?''
''These computations are hasty. The figures
announce d were based upon observations taken
very nearly together and at Irregular times
That is what makes such a variation In the
81 statements Of astronomers 10 different parts Of
the country. Nothing sure can be known until
time has been allowed for careful OBSERVING"
In addition to the observations taken On the
transit" glass by which the mathematical
proportions OF the comet are ascertained, some
very interesting experiments with the spectre
scope are In progress.
A LUCKY PARsoN.-Tbe Rev. DR.. N. W.
Csnkling, pastor CT the Rutgers Presbyterian
church. New York arrived