New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1878-08-31
JUpIrER AND HIS SATELLITES.
From The SENT Weekly Tribune. Auoaa2s.

From The SENT Weekly Tribune. AWoast29.
During the month Of September the giant
planet Jupiter iayOraby placed fer observing SINCE
he souths at 917 D. M on the LIST inst and at 720
or the 3Oh and thus his greatest altitude in the
early hours Of the evening With small telescope
the varying phases Of his satellites constant source
of delight 10 the young astronomer. sometimes they
are eehpsed by passing into the shadow OF Jupiteri
at others they are oceulted by going behind the
disk Of the planet Again they pass across the
planets face followed by the transits of their
shadows These eclipses. oceultations and transits
always add greatly the interest OF observations OF
Jupiter. When the satellites from east 10 west
they pass between Jupiter and the Earth, and give rise
to ransts and shadow transits the ngress and eress
Of which be noted with fair amount OF exaetness
When they pass from west to east they are moving
along the superior parts Of their orbits and occulted
or ecpsed according they disappear behind the disk
of the planet plunge it's shadow Before Jupiter
is In opposition the eclpses all the west right
hand side Of the planet; after opposition, the east
cfthand side. seen by direct vision In an inver
ing telescope these positions Of course reversed AS
Jupiter in opposition in July last, his shadow now
falls TO the east and the ecpses all happen on the left
hand side The first satellite THAT nearest JUPITER
passes into the shadow while stu behind the disk Of the
planet so that only it's temperatures after an eclipse
are visible The second satellite sometimes be OBJ
served to disappear well Teappear, while IN the
case Of the other satellites both these phenomena
are usually observable.
The times the ecpses OfJupters satellites have been
very carefully calculated and recorded in tables for the
purpose of helping sailors travellers to find their
longitude They are also useful, where the Longitude is
already known in giving correct local time In fact one
of these processes the Of the other although
neither furnishes very accurate results An Illustration
will show how this is done. Suppose traveller in the
United States notices September that the fourth
satellite of Jupiter reappears after being ecpsed at ex
actly sh 44in. As p IN. local time. Turning to his
almanac he finds that this temperance took place at
IOh. l5m POS Washington time. He sees at once that
he is west Washington and simple operation IN sub
traction tells him that the difference Of longitude in
time between him and the capital is exactly ILL., SIM
25s which is equal to 900 81 49, Of arc 15o cores
ponding to ! hour His longitude therefore, is 900 81
l5H west of Washington, go 81 81" west of Green
wieh.
Now suppose person in Boston, knowing his long'-
tude in time be 23m. 41.5s later than Washington
wishes to ascertain his local time Turning to MS
almanac he finds that September the first satellite
of Jupiter reappears after being ecipsed at Oh en- lSs
D. M Washington time Adding TO this the difference In
time C23m. 41.5s.l between Washington and Boston,
gives him Oh. 29m 595s-practically half past p M
as the Boston of the temperance Of the satellite
The following table gives the principal phases OF the
ffg~m- IL In awfnV reeY