Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1889-06-10
ABOUT ECLIPSEs.
PittsburEers Will Not Have Solar Eclipse
Until 19OO-The OccuItation of Jupiter
An AuuuIar ErIiv.. rh;s Monsh

Untii l0OO-The OccultatiOn OF Jupiter
An Annular Eclipse This Month.
Probably no astronomical phenomenon en-
joys more attention from the general public
than an eclipse. If they were of more frequent
occurrence the novelty would likely wear on,
for familiarity breeds contempt" and they
would not be events of such interest. No doubt
every one has seen an eclipse of the moon, but
probably there are many who have never wit
messed solar eclipse, and yet, paradoxical as
1t may at first seem, solar eclipses occur more
frequently than lunar eclipses, in the proper
tion OF Al to 20. The reason that so few eclipses
OF the sun are seen in any given place is that a
solar eclipse is visible to only small portion
of the globe, the central eclipse being visible
to belt of country only few hundred miles
wide and few Thousand long. This Is due to
the fact that the moon is much smaller than
the sun and casts only a small shadow on the
earth, while if it is the moon that is eclipsed,
the eclipse is visible wherever the moon is WIS.,
ible.
The next solar eclipse of any considerable
size that can a be @ seen in Pennsylvania will oc-
cur on May 26, 1900, which will be total in GER
tain portions of the South. So we must either
be patient or adopt Mahomet's principle, as
astronomers do; If the eclipse won't come to
us, then we must go to the eclipse, and If we
want to see the eclipse that occurs this month.
we must go to South Africa or the Indian
Ocean, and thither the astronomer would go,
as is his wont, if the eclipse were of very great
importance.
But the eclipse Is only "annular." Ian annu-
lar eclipse occurs when the moon isn't big
enough to cover up the whole of the suns disk.
and at the middle of the eclipse leaves ring
around the edge of the sun unobscured
When one body revolves around another, it
always does so in an elliptic orbit-a circular
orbit would be unstable-and so the distance
hafru 10 foIIn In
case of the moon, her distance from the earth
varies from 22l, ,00O miles to 100000 miles. The
diameter of the moon is 2 l50 miles, and that OF
the sun $50 900 miles. 1t may easily be seen, then
Especially with the aid of diagram which
the reader can construct), that the shadow
cast by the moon into space is a conical one;
the point of this cone is on an average about
234, 600 miles from the moon. To any person
within this conical shadow. then, the sun will
be totally eclipsed; but if, as in the present
case the moon is more than 234, 600 miles away,
an observer on the earth will be outside this
completely dark space, and VIII see the sun
eclipsed only partially or not at all. At the
time of this eclipse the moon will be 25l, 600
miles away; the black shadow will therefore
fall far short of the earth, and the sun will not
be entirely obscured anywhere. Another and
simpler way to explain an annular eclipse is
that the apparent diameter of the sun is 81 S''
and that Of the moon 2y 24', and therefore the
moon will not succeed in covering the whole
disk of the sun.
This solar eclipse will occur on the 2sth of
the month, and be visible in portions of the
South Atlantic Ocean, South Africa and the
Indian Ocean as an annular eclipse. and as
partial eclipse to a large part of Africa. parts
of Arabia and India, and the whole Of the In
dian Ocean.
The main point of interest about a solar
eclipse, which astropomers travel to the utter
most parts of the earth to see Is the corona.
This is something that probably can only be
seen during total eclipse OF the gun. 1t usu-
ally appears as a bright halo surrounding the
sun, about as wide as the diameter of the sun,
with fantastic outline and silvery white
color To explain all about the solar corona
has long been problem with astronomers.
Some have thought it was simply an optical ef-
feet produced by the light Of the sun being
diffracted by the edge of the moon. 1t is now
pretty well established, however, that the CO.
roma is the suns atmosphere of matter shining
probably by reflected solar light. On account
of the brilliancy of the suns light, the corona
is only visible when this light Is shut OF by
total eclipse and as the light is not altogether
shut off by this annular eclipse, the corona will
not be visible.
About all of interest for the professional
astronomer in this eclipse would be obserya-
tions of the times of the four contacts, l. the
times when advancing and following edges of
the moon are coincident with the edges OF the
sun, and this is not OF sufficient Importance to
will have to wait until December q, on which
date an eclipse of the sun will occur which will
be total in portions of Africa and the South
Atlantic and islands just north OF South
America.
Eclipses of the sun and moon usually occur
In pairs, about half month apart SO in the
present case the moon will be eclipsed on the
18th of July, but the interesting phenomena
will not be visible in the United States. 1t
may be seen generally in Europe, Asia, Africa,
Australia the Atlantic Ocean and the easterly
portion of South America.
Though the moon seldom gets a chance to |
hide the sun from view, it frequently passes |
over fixed stars, and occasionally over planet.
To observers in our neighborhood, about A. |
M. on the morning of the 14th. the moon will |
pass Just south of Jupiter and farther south on |
the eartt's surface the moon will. of course, |
appear to be farther north, and will pass over |
Jupiter, making an occultat1on to those In |
more southern latitudes. |
Two small stars will be occulted this month, |
which NAV be seen with moderate telescopic |
power here. The first is Sc Aquarii, a star of |
the sixth or seventh magnitude, which will be |
occulted by the moon. The star will disappear |
behind the bright side of the moon about 1s5O |
A. M. on the morning of the 18th, and will re-
appear about an hour and ten minutes later |
from behind the dark side. On account of the |
brightness of the moon, the star will not be |
well seen In telescope OF less than two or three
inches aperture. The next star that will be oc- |
Quilted is ''B. A. G. H." star Of the sixth mag
nitude in the southern part of the constella |
tion Pisces. The moon will rise with the star |
be hind it, but the star will appear on the west
side of the moon, 10 or 10 degrees north of a |
point on the moons edge directly west, at about
l30 A. NJ. The observer must watch intently |
to note the disappearance or reappearance of |
the star as nothing could be more surprisingly |
sudden than the complete extinguishing Of the |
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