The morning call., 1894-11-10

order that observations may be of astro-
nomical value. a telescope of at least two
inches aperture, with a magnifying power
OF at least thirty diameters should be used,
and the exact time of the interior contacts
of the planet and sun both at ingress and
egress should be noted. The external con-
facts need not be observed except by those
who have comparatively large telescopes.
10 order to know where to look for the
ingress of the planet, the observer should
find in the field Of view of the telescope
the north and east points of the suns
border and estimate from the north point
an angle of SO deg. At this point the in
gress will take place. The telesco pc should
give a sharp image Of the suns edge. H.
ternal contact will occur about two
minutes after the planet has made a notch
tact. as also the time when the contact has
passed and the first thin thread of sun
shine become visible between the planet
and the suns edge, should be carefully
noted. The watches used during the OBJ
servations should be compared with the
Lick Observatory time, and observations
sent 10 the Lick Observatory should COM
prise the rough otes as we'll as fair
copy and the watch comparisons. As COM
puted for the Lick Observatory, the transit
begins at hours 50 minutes and seconds
A. NJ. Pacific standard time, and ends at
=
owing to probable inaccuracies in the
tables the time is likely to be somewhat in
error.
Professor Davidson has computed the
times Of contact for the Davidson Observa-
tory as follows. Pacific standard time:
First contact. external. Z :55: 70 A NJ.
Second contact, internal r :67 ~ A. NJ
Third contact external .............l :l0:28 P. NJ.
Fourth contact internal. 1:l2:l2 r NJ.
Mercury will enter the suns eastern
iirfnh dnn min ooof Of fhA
lowest point Of the SUD, and emerge from
the western limb at 68 deg 20 min. west
from the suns verteX. and its path will be
about one-eighth of the suns diameter
above its center. Owing TO the small size
of the planet % compared with the sun.
Mercury will in transit appear as a very
small, round and intensely black spot. but
| without any resemblance to the sun spots.
Il will be a matter of interest TO deter
mine whether the planet can be distin-
| guished before it touches the limb of the
sun by fine circle OF faint light around it
wholly or in part. This aureola may pos
| sibly be seen, too, when the planet has
progressed half its diameter en- the suns
! disk as also at the third and fourth con-
facts. Similar phen omena were observed
| 10 1882 at the transit of Venus. The times
of contact, as computed from the Ameri-
| can Epbem iris and the Berlin Jahrbuch,
| differ, the latter being later, so the OBJ
server must watch for the contact at the
| earlier predicted times. For the benefit of
the scien tifically minded 1t may be stated,
quoting again from Professor Davidson 8
| notes, that "at the computed time of first
contact the right ascension of the sun is
| 10 b. min. 14.62 sec, and the decliuation
| south II deg. 16 min. and "a Sec, while tn 9
| right ascension of Mercury is 10 hours.
There are not many scientific deductions
| to be gathered from the observations OF
the present passage of Mercury across the
suns disk. Though the data can be used
10 determine the earth's distance from the
sun, still that fact can be arrived at In a
much more satisfactory way from the OBJ
servatIons of the ;ransits of Venus and by
other calculations. However. it will give
astronomers the opportunity to correct the
tables of the planet Mercury, thereby sup
plying a more accurate basis for mathe-
! NAUTICAL calcul atoms. The observations,
too. NAV set at rest the theory of the
French astronomer, lie Verrier, about the
| motion Of the perihelion of Mercury, and
also the existence of cause of perturba-
ton between the planet and the sun. In
the transit of 1878 Professor Langley of
| Allegheny failed TO see the "back spot"
| or ligament on Mercury. as also the CEN
trail bright spot and the aureola around
| the planet. These are minor results, but
all may be determined by the observation
| If this transit for which scientific men are
better equipped than ever before.