PRESENT
ASPECT OF JUPITER
I
am glad to be able to report that observing conditions generally have
been very good with us since the beginning of last month, and that at
least one other member besides myself has taken advantage of the good
seeing to make drawings of Jupiter. I am unfortunately divorced from
my observatory for some months, but have with me in the country an
excellent 5-in. Cooke altazimuth as well as accurate time.
I
have never hitherto prosecuted a careful and continuous study of the
giant planet's surface, and confess to great surprise at the vast and
rapid changes that become apparent. This especially struck me first
in the case of the N. equatorial belt, the northern and equatorial
components of which exhibited alternately dark masses and
condensations, divided by white spots after intervals of only five
Jovian rotations. On March 13 and 14 there were typical instances of
this. On March 26, 20h 40m, G.M.T., a faint wisp across the equator,
was conspicuous, and next night, March 28, 2h 20m G.M.T., was
invisible, while the equatorial region near the c.m. showed
considerable change. Definition excellent, 4 to 5 on both occasions,
power 200. The N. temperate area, however, has puzzled me most, for
the three belts often seen have varied much both in visibility and
latitude, while with exquisite definition on April 1, at 0h 20m
G.M.T., the following portion seemed overlaid with vapour of a sage
green tint, and the belts (2) were only faintly visible in their
preceding parts, The Red Spot has been well seen on several occasions
of almond shape, the f. end slightly more pointed than the p. Its
tint seemed uniform, and a very delicate brick red, like a faint
stain. It is overlaid on the S. side by the S. temperate belt, which
is closely double through nearly its whole extent, and f. from the
centre of the Red Spot is much darkened and sinuous. The great spot's
preceding end was estimated on c.m. at 1h 15m G.M.T., April 1, and
the following end on c.m. at 21h 52m 36s G.M.T. of same date. In the
transit of Satellite I. on February 22, observed at Waverley, near
Sydney, with my equatorial, the shadow must have been occulted by the
satellite, which is perhaps worthy of note.
WALTE R F. GALE .