Evening star. [volume] (Washington, D.C.) 1854-1972, 1881-07-02
OBSERVING THE COMET.
How the work In Done n tho Oh.
neutrality-suspicious. Its Position

NEUTRALITY-SUSPICIOUS. It's 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
full emens OF evil, but now methodical sciencs
inspects them as coldly as physician would
view an unusual deformify or naturalist In
ve5tigate some new found species OF antma
life. The present comet instead o. trgnteatng
people, has only excited their curiosity Every
one wants to see it, an1 to learn all the facts
about IL. BE grumoles Ii earerul and deliberate
scientists are unwilling to answer hts questions
at dice. This curiosity has attracted an uuJ,,
suai number OF visitors to the Ooseryatory
during the past week.
observations are taken OF the comet az they
are TAKEN OF any other heavenly body. though
tnere Is an exciting interest in the work which
relleVeS IL or any sense OF drudyery. An as.
tronomer
ON The LOOKOUT FOR COMETS
uses generally small glass,-one that he can
handle easily and which has broad field. Tae
comet, having been discovered the first point
to be determined Is its position,-its right as
cenSion and declinat10l corresponding to the
Longitude and latitude, OF a point on the face of
the g lobe. When this has been determined,
and three observations taken at euui distant
ttmeS,-aooue week apa 1.-THE astronomer,
Dy series OF computations, is enabled to de-
termine very accurately the elements OF the
orbit, from which 1t is an~easy matter for
him to compute the size, distance from
the earth and rap1dity Of motion of the ,m It.
Perhaps he may be enabled to make q pre1tc
lon as to when 1t will return. Tless oo3arva
lois are taken on
TEE 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 Ooserv-
atory. There is an opening through the roof
and in the north and south sides Of the square
structure, looking as though some one had C It
slice from the middle OF 1t. The glass inside
q g 1fv1 tnly
It, so that as It is revolved from north to south,
IL never SWelves hairs breadth to wards the
east or west. star seen through 1t, Is SUD-
supposed to be exactly over the meridian line.
BY this glass the right ascension and decl1na-
ZION or star, planet or comet, is ascertained.
In case OF strange body, II its approXt-
mate position In the heavens is known.
and that can be determined with the
naked eye, before it reaches The meridian,
the glass is set SO as to cover IL wnen
1t crosses. On either side OF the glass are
large wheels, which reyolye With the glass.
These wheels are sealed and graduated 50
finely that microscopes have 10 be used to read
the measurements. Presuning that the Ia.
strunent has been set right, the observer
when he expects the star or comet, peers
through the glass. The Held OF the glass Is
crossed up and down With fine lines In several
grOups OF two. three ana five There are also
TWO i1ne hair lines from right to left.
THg OBSERVER
has in his hand Geographic key, which con-
meets with an electric chronograph. When the
comet enters the field of the glass, as 1t Gro Ses
each line, the observer taps the key The two
horizontal hair lines are adjustable by means
or little screw in the eye piece OF the ino6ru
the center Of the nucleus Is exactly be6waen
the lines. The comet Is not greatly magn!
Ted in The glass, but is very clearly de-
ne exe6 hf1s a ps front to- na be head ea
point where ne tail seems to split. When the
comet bias passed over the meridian at It's lower
elimination. which II does nov little after II
O'Clock at night, the observers work really
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.
eEces OF varying temperature, With nothing
but its face showing. 1t keeps sdereal time.
The hour aud minute taken from the clock. and
the records made by the chronograph. give
down to the tenth part OF second the lime
That the comet crossed the meridian, the cen
tral Hne on the field OF the glass representing
the meridian. The time of the passage is easily
convertible to right ascension, Or, In other
words, TO s1dereal longitude, just as the longi-
tude OF town can be calculated by owing
Its time. The register or scale On the wheel on
a little register connected with the screw regu
let1ng the horizontal lines on the field of tAe
glass, Indicates
THE ZENITH DISTANCE
OF the body observed, which Is readily convert
able into decilnatton or sidereal latitude The
chronograph should be described here. in order
70 give correct idea OF the accuracy With
which the time can De determined. II consist 9
OF revolving cylinder. covered with sheet 0 I
paper, so placed that an iron from al electric
apparatus makes marks at regular Intervals
The apparatus Is celicately adjusted, so that
the interval Is exactly second. The tapping
OF the key held by the observer makes an extra
marx, and any school boy would soon learn 10
tell. by means Of these arks the ex ac1 r!n. al
n.sS ga
the right ascension ana declination Ia tbs M au-
ner described, he really has just commences
Ills Work. he has before him the tedious ta5g CT;
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 O!
cience are used In mounting aud adlu,tuy
these meridian glasses, it is found that they
are so seldom accurate that astronomers
always take ihfor granted that hare are some
errors In figures first obtained. A deviation OF
hundreoth part OF hairs breadth could
hardly De detected on the earth, but where the
line OF vision extends millions Of miles into
space 1t Is apt to seriously affect nice calcula-
tons SO the astronomer begins series OF
intricate experiments and calculations to cor
ment. The instrument is tested with a fine
level Underneath, set upon pillar which Is
built upon the ground and is Independent OF
me observatory building, is pool or trough
himself that the instrument when placed per-
pendtcularly points directly to the zenith. must
first see the lines on the neld reflected back
from the mercury. SO sensitive is the mercury
to all disturbances that II wagon is passing
near the building the surface IS so disturbed
That no rejection can be seen at all when look.
Ing through the glass The observer having
corrected the errors by long and tedious COM
putatlons, fually obtains a correct statement
OF the position OF the comet. After taking
three such observations. week or more apart,
ne Is ready to compute the elements or the
comets or blt.
AN ASTRONOMERS LIFE
ut Is popular Idea, said Mr. Winlock, the
astronomer who explained the method OF TAX
Ing observations to STAR reporter, that an
astronomers life is a poetical one-that all he
has 10 do is TO contemplate-gaze through g
glass and think. There Is considerable drtldp-
cry and sameness about observing"
"Can the COMPUTATIONS so far made about the
comet be cOrrect:'
''These computations are ha5ty. TIE figures
announce q we're based upon Observations tax an
very nearly together ana at Irregular times
That is What makes such q variation In the
statements Or astronomers ia 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 tie come. are ascercained some
very interesting experiments With the spectro.
scope are In progress.
A LUCKY PARSoN.-The Rev. DR.. n. W
Cenkl1ng, pastor OF the Rutgers PRESBYTERIAN
chuTch. New York City, has recently arrived in