The New York herald. [volume] (New York [N.Y.]) 1840-1920, 1877-08-23
: ASTRONOMICAL.
The Total Eclipse of the
Moon Tonight.
PHASES OF THE PHENOMENON.
Professor Halls Discovery Of the
Satellites of Mars.
MEASURING THE LITTLE MOONS.
observations Of Their Orbits and Distances
From the Planet.
OFFICIAL ANNOUNCEMENT OF fHE DISCOVERY.

OFFICIAL ANNOUNCEMENT OF fAE DISCOVERY.
THE TOTAL ECLIPSE OF THE NOON
THE SATELLITES OF MARs-AN OPPORTUNITY
ron MEASURING THE SUMS DISTANCE PKoM
THE xARTH-rHE PLANETS.
70 THE EDITOR OF THE HERALp:-
Although the total eclipse Of tho this evening
Will occur at so carly an hour that In Now York city
and to the west Of only the end Of the eclipse will
visible will take the occasion for calling attention TO
various astronomical news OF interest
The moon will rise totally eclipsed ~ nine minutes
before O'Clock p NJ, and win begin TO emerge
from tho shadow three minutes after O'Clock
that It will require ciear horizon to Its FIRST
appearance The moon will have entirely left tho
shadow Of the earth four minutes after eight O'CLOCK
while still hardly above tho tops OF tho houses Tho
penumbra for another hour, will continue to over
shadow the moon but its effect will be hardly apprc-
siable, merely slight dimming Of its light Before
leaving the moon will remark that "Kcy's Fatten-
,ngs" diagram Of which published In the HERALD
" February 8, 1876. have latciy again been secn,
although worry much loss than half extensive as In
aicated by the dscoverer and IL appears that Of
tho dcprsssiens caused by the ring Ansgarus and
Behaim, and another by Xasstner When Iteration
brings them to the edge Of the they appear per-
Iectly straight and Hat. "a 1ssr &c tts eissi
sArELLIr8s MARS.
About seventeen degrees cast OF the moon, easily
visible by ton O'clock will DO bright STAR which
ls tho planet Mars This planet 10 attracting partcu.
lar interest At this time for two First tho
great astronomical discovery OF Professor Hail. few
days ago, Of two satellites revolving around IT,
Tho question asked why these wore not discov.
erAA lSofn Tho To- nrt ho
cessivo smallness OF these little moonA Even now,
whom Mars s nearer to us than 1t has been for years.
q telescope with aperture OF nine inches would only
show them, If at all, in clear sky. and In tho alb
ssnce Of the light of tho planet itself Ordinarily
under tho most favorable circumstances, there have
boon few telescopes hitherto by which they could posi-
bly, be seem and thoy could not have been unless
looked for specially and often enough to insure their
being At favorable distance from the planet Burrss
tended by satellite It Is too small to DO seen by tho
most powerful telescopes" And then follows. in
umacs OF the asteroids known in 1885, which is ono
and halt times the distance Of Mars from nd only
sUS miles IN me open space
body 70 point out we may reasonably conclude that
W6po those who alone had the means TO detect them
that satellites existed that they instituted
rigorous search for them. Now that they have been
eight magnttudes smaller than vesta This would cor
respond, at the distance OF Vosa, to onefortich its
diameter But. being three times as near. - this tmo
that reduces the diameter again 10 onc-third. We
must allow one-haf for their being the SUM-
therefore more strongly illuminated. So that ASSUME
oil Mars OF equally reflective substance their diameter
cannot mach exceed thrcc miles. little moon like
dsmaec than 'tidal wave The wonder is that such
= little specK should have been ut all moro than
thirty million Mules away As the scale Of magnitudcs
Is not yet thoroughly settled among astronomers may
DO that the estimate Of rhrteentl fourteenth mag
nitude" corresponds to star still smaller than this
that possibly there has been hitherto no telescope ex
ecpting the giant refectors capable OF showing the
satellites under the most favorable circumstances.
II usually takes much more optical powcr 10 make
discovery than to verify IT. and now that the exist
ence and position OF the satellites known
who has small telescope will be looking tor them.
shall not be surprised II many people see them with
telescopes Of moderate apertuEcs and many more will
think they soc them with small telescopes II not with
tho naked sys For instance, on tho 1911 my atten-
ton was attracted, IN looking ~ Mars, by small
following 1t, and quit, TO n This u ninth
magnitude slar and thcre will hardly be another op
portunty during the present opposition TO see so
bright star so near. But 1t is not improbable that
thorc are smaller stars lying in the track of Mars
which may DO seen by observing with care, and which
are liable TO DO mistaken for the satslIi,es But mo-
matter how small tbe satellites are, they will
important use In astronomy. in determining the mass
which II causes In tho motions Of the other planets
SUNS PARALLAx.
The other reason why the planet Mars has now for
peculiar arises from ils sGordng
y means Of correcting the suns distance from tho
earth. The transit OF Venus OF 1874 has proved par
tial failure for the reason that she atmosphere OF
Venus made impossible determine the exact times
Of the several contacts Mars docs not approach us
nosr as Venus was at the time of the transit but in
the case oil Venus all that could observe was the
difference between tho parallax Venus and that of
the SUM- whereas In tho observation Of Mars compar
ing with liked stars, which have parailax, can
deteAmiue the whole parailax When add tho
much creator ease ot observing and tue fact that
observations can be extended over period OF nearly
Two months We see that there Is TO hope for
better results from the observation OF Mars during
us present opposlion' when II WIN DO nearest
Is nearest the sun and when the earth IL
furthest from the sun, than have been obtained from
tue transit OF Venus. Mr. Giu, with u heiometer
loaced by Lord Lindsay, is observing Mars IRON tho
Island OF Ascension, oil the west OF Afrlca-not
because tho observations cannot DO made elsewhere
because that place Is In the latitude favorable for
The purpose. the greatest paralax would be obtained
BY observing from tho Equator, where tho motion OF
The observer between the observation in the evening
and that IN tho following morning, from the rotation
81 tho Garth, IL greatest. But as Mars Is Tow
degrees south OF the celestial Equator this paralax
would not DO wholly IN right ascension, SD that by
lectng place few feet south Of the carth's Equator
while The total parasx Is not much csscncd, IT Is al
most wholly confined to parallax in right ascension
AMI better adapted to obtaining the final result.
t..tr THE PLANET SATURN
About five degrees north Of tho planet Mars will be
seen another star, much less bright THIS The planet
Saturn. II has been stated that Mars Is IN conunc
hon win Saturn during the prcscLt year three times
out 10 the old method OF reckoning conanclious this
not true, for Mars does not roach the longitude OF
odtuIu AZ July UT august, Out only on
November 8 when their distance Will be only one
third the moons diameter Saturn is always an III
cresng telescope object but at present IL IL partic
ularly in consequence OF tho nsrrowncss Of the
rings which arc ncarly cdgcwsc to present
tho appearance Of fnc straight line piercing The bail
OF tho planet Tho rings will totally disappear next
February and alter the conjunction with the SUI IN
March, the southern side OF the rings viii DO illumn
ated and come gradually into vicw
JUPITER, vxSUs AND NERcrRy.
me night star Ia the south about sunset Is the planet
Jupiter IN the west. setting about an hour alter tho
sun, Is the planet Venus. Thesc two planets will
gradually approach each other and viii be In CON
uncton as evening stars in November anu lew weeks
alter Jupiter Will disappear IN the western twilight.
About four degrees west OF Venus the planet Mer
curry, but II Is too low 10 be readily founi.
D'ARIEsr's COMET
The three comets which some months ago appeared
simultaneously have all disappeared. There is only
ono comet nov visible, the per- odca comet discovered
by p'Arrest in lo5l having pcrod Of ak and a hall
years II was discovered on July ., and may be seen
In tho morning SKY, but is too faint to be WITHIN the
reach Of ordinary telescopes
HENRY n. pARKHuRsT
New York, August 70, 1871