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                 THE ROYAL ASTRONOMICAL SOCIETY OF CANADA

                                                                  Bulletin No. 11

                              PLANETARY SECTION

Summer has passed and now the Centres should be starting their programs again. We
hope these will include observing the planets.

MARS:   Drawings of this planet made during the recent apparition would be appreciated
as arrangements have been made to exchange observations with the Mars section of the
British Astronomical Association.

SATURN  is getting higher and higher in the evening sky and it is hoped our observers
will again don their parkas, mukluks and other paraphernalia and brave the elements!
Observing Saturn is very valuable as it is the amateur who keeps track of the surface
detail. (See Bulletin No.9 for observing hints.)

JUPITER should be having our attention, too, as it is observable in the morning sky for
early risers. Timings of Satellite Phenomena are very important, especially since the
Observatorto do Valongo in Brazil is depending on us.

A startling fact has been deduced from your observations, as is shown in the following
section. Comments and further observations are invited.

CALLISTO AND THE SOUTH EQUATORIAL BELT OF JUPITER

During the first half of 1969 much attention was given to Jupiter by the observers of the
Planetary Section. In response to these Bulletina several hundred drawings were sub-
mitted by Barry Sherman (Hamilton), D.R. Moore (Edmonton), Tom Tothill (Ottawa),
George Haeckel (Edmonton), John Garden (Hamilton), Richard Newman (Edmonton), John
Calder (Gait, Ontario), Paul Deans (Edmonton) and myself. A result of the analysis of
these drawings is that there appears to be a correlation between the intensity of the
South Equatorial Belt of Jupiter and the position of the satellite Callisto.

On certain drawings of the planet, the S.E - B. was very dark. Sometimes It was shown
as being split into two dark components and, In other drawings It was either very faint
or missing altogether. The co-ordinator arranged these drawings in chronological order
with a view to determining when the Belt was visible and when it could not be seen.
It was amazing to discover that the Belt varied with a period of 16 days. This is very
nearly the orbital period of Callisto (16 days, 16 hours, 32 minutes) given in the
OBSERVER'S HANDBOOK.

The elongations of Callisto and the intensity estimates were formed into the diagram
which follows.  Each dot on the diagram indicates an observation. Lighter intensities
are at the bottom and darker ones at the top. The curve represents the position of
Callisto.

It can readily be seen that the Belt was darkest when Callisto was at Western elongation.
It was characteristic of the Belt to darken gradually, split, and then fade rapidly as the
elongation passed.

Is this a coincidence?  If so, it Is an amazing one!  It deserves the attention of all
members of the Section, professional and amateur alike.

(Diagram here.)



W = Western Elongation
E = Eastern Elongation

Western Elongations:   March 17       Eastern Elongations:  March 25
                       April  2                             April 10
                       April 19                             April 27
                       May    5                             May   13
                       May   22                             May   30
                       June   8

References: SKY AND TELESCOPE, Vol.37
      No.3 (March 1969) page 201
      No.4 (April 1969) page 265
      No.5 (May 1969)   page 333
      No.6 (June 1969)  page 401


                                   THE LAST WORD

Certainly, the foregoing shows that valuable work can be done by the fellow with the
modest instrument; most of the observations were made with 4- and 6-inch telescopes.
We trust that each Centre now has an observing group and will appoint someone to sub-
mit observations on a regular basis. (They will be returned promptly after being copied.)
As only three Centres have NOT yet been heard from, it appears that our program will
bear results soon, (Is your Centre one of the silent ones?)

NOTE: To Centres in Ontario and Quebec - I am prepared to visit each of you for a week-
end and give a talk on observing or give tips on how and why we should observe. Just
write or call!
                                                        Kenneth E. Chilton,
                                                       National Co-ordinator,
                                                        Planetary Section,
                                                  93 Currie Street, Hamilton 57, Ontario
28 October, 1969.                                       Phone: 416-388-0586.
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Planetary Section Bulletin No. 11
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