The morning call., 1891-09-20
WHAT CAN Be SEEN
IN THE HEAVENS.
Celestial Phenomena Visible During the
Present Month.
Opposition Of Jupiter-Tha Harvest Moon-Dis-
appearance Of saturn's Rings-When to
Look for Mercury-Fixed Stars.


of considerable interest to the student OF
astronomy, if not to the general reader
The most important events of the month
will be the opposition of Jupiter on the
9Th, the disappearance Of Saturn's ring on
the ODD, and the arrival of the sun at the
autumnal equinox OH the 23d. writes a cor
respondent to the Pittsburg Dispatch.
Jupiter Is now In the constellation Aqua
RUS the Waterman, and is the most brilliant
and conspicuous OF all the planets. On the
evening of the 9Th he arose at 6:25 o'clock
at point 1Oo south of east His angular
diameter was "A" and viewed with te'e-
scope magnifying forty times would appear
as large as the moon does to the unaided
eye. Jupiter being on that date at his
shortest distance from the earth, was at
his brightest, and the present month
will be the most favorable time for view
ing his satellites, which may be seen
with an opera-glass OF small telesco?e. At
4 80 o'clock in the afternoon on the 9TH,
which is the exact time of opposition, Jupi
tors position in right ascension was 22h.
59n. 0S., and his decllnati0n was deg I'm.
50s SOUTH His motion at present Is retro
grade or westerly, and will continue to be
so until November Sd, after which it will be
direct or easterlv, and in the order OF the
signs of the zodiac. Jupiter and the moon
were in conjunction on the 18th at 12:27
o'clock in the morning, the planet being
deg. 45m. north Of the satellite.
THE HARVEST MOON.
The phenomenon commonly known as the
harvest moon" was q prominent feature of
September's celestial exhibition. At the
time of the full moon, which occurs nearest
the autumnal equinox, the moon is observed
to rise but little later each evening, so that
the number OF consecutive moonlight even
ings is greater than at other seasons OF the
year.
The reason of this is that when the moon
is full in the autumn, it is always moving
nOrthward, and is in that part of its orbit
which inclines least TO the horizon, and
when it is full in that part of its orbit, 1t
rises less than half an hour later each even
ing, whereas the average daily retardation
is about fifty-two minutes. In the spring,
when the moon is moving southwark at its
full phase and its orbit inclines most to the
horizon, it rises about an hour and quarter
later each evening, and the number Of con-
secutive moonlight evenings Is less than
the average. 1t will be readily understood
that the nearer the moons orbit is to being
parallel 10 the horizon the less IS its de-
scent in moving given distance. and the
less the interval between its rlSlngs on sue
cessive days. So, conversely, the nearer its
orbit is to being perpendicular TO tile hor-
ZOu the greater is the descent In moving
C.
stances the interval between the successive
risInes of the moon would be greater than
usual. In high ATTITUDES the phenomenon
of harvest moon is far more noticeable than
in P!ttsburE, while at the equator it is ell
tirely absent
THE AUTUMNAL EQUINOX.
On the sd of the month, at 2:45 o clock in
the morning, Pitt,burg time the sun reaches
tine halfway point between the sOlstces.
At that time, if we ignore the effect Of at
mOspherlc retractiOn, day and night are
equal throughout the Inhabited world. The
effect o. the refructOn Is 10 raise the sun
about 50 from its true place when in the
horizon, thus increasing the length Of the
day, or period of sunlight, in greater or
less degree, according to the latitude. In
the latitude of Pittsburg it makes differ
ence of but few minutes, but in latitude
So the length of the day. when tho suns
dec,inatOn is zero, is - h., Sc m, If we
consider the day 10 include the whole time
during which any pat of the suns disk is
above the horizon, so that the length of the
day is increased more than an hour by re-
fraction.
Practically, however. there is constant
day in that latitude Mt the time mentioned.
as the sun descended but a below the hori-
ION, so that there Is strong twilight all
night. In the north and south latitude 90,
or exactly at the poles, where there Is
perfectly parallel sphere, the sun at the
ll!llH Oh Tie eiuluOA NllNits SISdl aAbulu Nilo
horizon, touching successfully every point
of the compass. The sun when at either
equinox would rise due east and set due
west except within few degrees of the
poles, were it not for the effect OF refractiOn
before mentioned. AS it is, such is the case
only in the equatorial regions, but in moder-
ate latitudes it is approximately correct to
say that it does while in very high latitudes
such an assertion would be altogether
wrong. Thus in north latitude $50 the set
ting amplitude Of the suns upper limb. cor
rected for refractiOn, on the 22d of Septem-
Der is 10 from the west point toward the
north. The reason of this is that in very
high ATTITUDES the apparent diurual motion
is nearly parallel to the horizon, and the sun
or other heavenly body moves northward in
its diurnal course a considerable distance,
while descending the So which refractinn
refracted image disappears is several de-
grees north of where the real object sets.
sATURN's RINGS TO DISAPPEAR.
An event of considerable interest marks
the 22i of September and that is the dis
appearance from view OF the rings of
Saturn. At that time the plane Of the rings.
if continued, would pass through the center
of the earth. so il will be seen that only the
edge Of tie outer ring is presented to view,
which through the most powerful telescope
appears as an exceedingly fine thread of
light eXteu ding for short distance on each
6lUe OIL the planet. w men only lU6 eu9e OIL
the rings are turned toward the earth.
Saturn is considerably less brilliant than
when the rings are opened so as to expose
the fiat side TO view. Saturn viii, however,
be entirely invisible to the naked eye till
nearly the close of the month, on account
of its proximity to the sun. being in con-
junction with the sun on the 18th.
This Is certainly not good month for
viewing the planets, as only two Of them
are visible the majority OF the time. In tho
early part Of the month Jupiter has the
field to himself as the only visible planet.
Later on Mars becomes discernible in the
morning sky, rising heiiacally on the 18th.
Ii is so faint as to be very uuattractive, its
apparent diameter being only 3"9.
Mercury will be visible during the last
week of the month, but as it is then morn
ing star, it will probably have few observ-
ers. 1t is at its greatest el0ngation from
the sun on the 2Sth, at o'clock in the after
noon, and is then 10 SO distant from the
cent? al luminary On the morning of the
2Sth it rises at :23 o'clock, which is exactly
an hour and Dalf before sunrise the same
morning Its angular diameter at that time
Is Z" o, and half of its disk is Illuminated.
1t will at the time of visibility be in the
constellation Len, and will appear fully
as bright as all average star OF the first mag
Ditude. AS there are two bright stars close
together. visible from the 18th to the end of
the month, IL may be necessary to state that
Dllehbtl VI NiG lhU anu lllo Ouo tuC
higher up is Mercury, the other one being
Saturn, which rises heiacaly, or first be-
comes visible on the 2Sth. About 30 sepa-
rates them On the morning of tho 28th, but
they appear closer together each day, and
on the 30th are only 80 apart,
THE FIXED STARS.
The fixed stars Of the first magnitude vis-
BILE in this latitude at the present time are
Vega, Arcturus. Antares, Allan and Fomal-
haut, all of which may be seen any clear
evening. Those visible in the morning are
Capella Betelgeuse, Rigel, Aide baran, Pol
lux. Sirius and Procyon. Of those visible
10 the early evening. Arcturus is the most
brilliant, and it shines with ruddy glow in
the western sky. On the evening of the 10Th
it set at 9:46 at distance Of 26Ro north Of
the west point. 1t belongs to the constella-
ton Of Bootes the Herdsman.
Vega ranks as the second brightest star
visible in the evening, but it has a close
rival in CapeIla, which is yet so low down
early in the evening as to be somewhat OBJ
scured in the mists of the horizon. When at
a high elevation Car ella slightly outshines