January 6, 
a 
1923] | 
NATURE 

Our Astronomical Column. 
__ New Osservations oF Jupirer.— Mr. W. F. 
Denning informs us that Mr. Frank Sargent, of the 
University Observatory, Durham, observed Jupiter 
on the morning of December 24, and saw the 
hollow in which the great red spot is situated 
central at roh. 13m. G.M.T., which corresponds 
to a longitude of 239°-6. Mr. Sargent considered 
this hollow in the great southern belt decidedly 
more shallow than formerly. The great red spot 
appeared to be shorter than at the last opposition, 
its length being estimated as only 22 degrees. 
Following closely behind was the preceding end of 
the south tropical disturbance which made its transit 
at 2oh. G.M.T. in longitude 268°. The rotation 
periods of these two objects during the last six months 
were: 
‘Red Spot Hollow =gh. 55m. 38st. 
S. Tropical Disturbance =9h. 55m. 29s°8. 
These periods correspond very nearly with those 
derived during the earlier part of the year 1922. 
BaavDeE’s ComET.—This comet was observed by Dr. 
W. H. Steavenson on December 20 and 22. He 
describes it as follows: ‘‘ Magnitude 9 to ro, small, 
compact ; diameter about 1’; best defined in position 
angle 165°, rather diffuse towards 345°; there was 
central condensation, but no well-defined nucleus.” 
The brightness is only falling off slowly, and the 
comet is still within reach of moderate instruments. 
The following ephemeris, by Mr. Johannsen, of Copen- 
hagen, is very accurate. It is for Greenwich mid- 
night : 
R.A. N. Decl. 
hn m & 
Jan. 5. 22 55 22 19° 16’ 
ty | Be 23 4 30 18 46 
oe ise a3 X35. 30 18 18 
a yp 23. 221.22 17 54 
jp 21. 235°. $5.6 R7eor 
» 25. 23 39 «43 17 It 
The comet is crossing the lower portion of the square 
of Pegasus. It is desirable that observations should 
be continued as long as possible, in order to detect 
any deviation from parabolic motion. 
British ASTRONOMICAL ASSOCIATION sHANDBOOK 
FOR 1923.—Iwo years ago, when the well-known 
** Companion to the Observatory ”’ was discontinued, 
the Council of the British Astronomical Association 
decided to bring out the Handbook to take its place 
(London: Eyre and Spottiswoode, Ltd. Price 2s. to 
non-members.) Its aim is to supplement, not to 
supersede the Nautical Almanac, from which little is 
reprinted except the physical ephemerides. The 
riods of visibility of the planets are shown graph- 
ically ; details of important occultations, including 
four of Aldebaran, are given for 12 stations. Ephem- 
erides are given for Vesta, Eros, and D’Arrest’s 
Comet; it is hoped to extend this section further in 
future. The large-scale diagrams of the small stars 
near Uranus and Neptune will be useful for observers 
of these planets. otes are included on telescopic 
objects, lists of tests, ephemerides of variables, and 
in particular the dates of maxima of 27 stars that 
attain naked-eye visibility. There are also definitions 
and an extended list of astronomical constants and 
elements, which will be slightly varied from year to 
There are thus few observers who will not find 
book useful in their domes. 
NO. 2775, VOL. 111] 
ATMOSPHERIC DISPERSION IN PARALLAX WoRK.— 
One of the factors in the great improvement that 
has been effected in the photographic determination 
of stellar parallax has been the recognition that work 
must be limited to the neighbourhood of the meridian, 
where the effect of atmospheric dispersion is small. 
Messrs W. M. H. Greaves and C. Davidson have investi- 
gated the resulting correction to the parallax for stars 
of extreme spectral type in a paper read at R.A.S. 
November meeting. At 20 minutes of time from 
the meridian the correction for type By is -0*-009, 
and for type M +0%-005. These are quantities that 
cannot be neglected nowadays, so the necessity is 
emphasised for working still closer to the meridian 
where possible. 
The same difficulty is present in obtaining the 
solar parallax from photographs of Eros or other 
small planets, especially since the diurnal method 
necessarily involves considerable hour angles. The 
error can be diminished by using a visual refractor 
with a light filter, if the object is bright enough to 
permit of this. 
INTERFEROMETER MEASURES OF DOUBLE STARS.— 
The Astrophysical Journal for July has a paper by 
Mr. Paul W. Merrill on this subject. Mr. Merrill 
continued the observations of Capella with the roo- 
in. telescope at Mt. Wilson, and gives the following 
orbit from his own and Anderson’s measures : Period 
104°:022 days, a =0":0536, distance =126,630,000 km., 
parallax =0”-0632, masses 4:2 and 3-3 in terms of sun. 
He finds that the Greenwich measures in 1900 (on 
which considerable doubt has been cast) are fairly 
well represented on the supposition of a motion of 
the node of o°-9 per annum ; this motion is suggested 
by the interferometer measures themselves. 
The duplicity of « Ursa Majoris was independently 
detected with the interferometer. The magnitude 
difference is much greater than in Capella, but does 
not exceed half a magnitude. When Aitken discovered 
its duplicity in 1907-8, the position-angle and distance 
were 283°-2, 0-21; they are now 251°:3, 07-08. 
v? Bootis was also examined, but the results were 
more doubtful; the method is obviously a very 
powerful one in cases where the magnitudes are not 
too unequal. 
SOLAR PROMINENCE Activity.—Every half-year 
the Kodaikanal Observatory, India, issues a bulletin 
giving a summary of prominence observations 
during that period. The data for the first half of 
the present year in Bulletin No. Ixx. have just been 
received. The mean daily areas and daily numbers 
of the prominences are few, as was to be expected 
from the cyclical nature of the phenomena, the respec- 
tive figures being 3-17 (square minutes) and 11-05. 
Their distribution in latitude shows maxima in the 
belt 45°-50° in both hemispheres, and is very similar to 
that for the previous half-year ; this indicates that a 
new cycle of activity has begun in the higher zones of 
prominences. The statistics give further the distri- 
bution of prominences east and west of the sun’s axis, 
the activity of the metallic prominences, particulars 
of the displacements of lines observed in the spectra 
of the chromosphere and prominences, reversals and 
displacements of Ha and D,, and finally, areas and 
numbers of prominences projected on the disc as 
absorption markings. These valuable data are of 
great importance because they provide a complete 
record of the activity of the sun from a prominence 
point of view on a homogeneous system. 
