620713PlanetaryInst2_p1

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                           ROYAL ASTRONOMICAL SOCIETY OF CANADA
                                    Planetary Section

                        SPECIAL INSTRUCTIONS FOR OBSERVING JUPITER


     Instruction. Sheet No 1 contains information regarding drawings of Jupiter and
estimates of the intensity and conspicuousness of the planet's belts and zones. The
present sheet describes two important quantitative programs: the timing of satellite
phenomena and central meridian transits.

SATELLITE PHENOMENA

     Observations have shown that the phenomena of Jupiter's satellites predicted in the
Observer's Handbook are frequently in error by several minutes. The exact, nature of
these variations from theory has yet to be determined; timings to the nearest tenth of a
minute of occultations, eclipses, and transits can therefore be of value.

     Observations shouldbe, recorded on Form No 2. The satellite, type of phenomenon,
and predicted time should be recorded in the appropriate places from the Handbook or
Ephemeris. The observed times of first and second contact should be `recorded in the
centre section of the form. In order to distinguish clearly times of interior and
exterior contacts, a high magnification is recommended. Note should be made on the back
of the form if anything unusual is observed.

CENTRAL MERIDIAN TRANSITS

     The timing of transits should form the majcr part of every observer's Jupiter
program. The nature of this work is described in the Journal for April 1962, p.p.79-80
(copies available from the writer). The following additional information will be found
useful by the prospective transit observer.

     Form No 3 or its equivalent should be used. to record observations. Universal Time
is preferred since it usually avoids a change of date during a night's observations.
Trans its should be, assigned consecutive serial numbers through a given apparition. The
description should begin with a two-letter code indicating whether the marking Is dark
(D) or bright (W) and whether it is the preceding end (p), centre (c), or following end
(f) which is on the C.M.; this should be followed by a more detailed description using
the nomenclature given overleaf. The location is given in terms of the belts and zones.
At first the beginner may find it helpful to supplement his descriptions with a simple
sketch. Observers are urged to calculate the spot longitudes themselves using the
central meridian tables in the Handbook and the ancillary tables given below. To be of
fullest value, observations should be submitted fortnightly.

     To keep errors to a minimum, one eyepiece should be used conslstently, and an
attempt made to keep the line of the observer's eyes parallel to the belts. The observer
should record only features of which he is absolutely certain; erroneous observations
only make the longitude charts more difficult to interpret.

                      Change of Longitude in Given Intervals of Time

     System I:						System II:
      h   o       m     o     m     o        h    o      m     o     m    o
      1   36.6   10    6.1    1    0.6       1	 36.3   10    6.0    1   0.6
      2   73.2   20   12.2    2    1.2       2	 72.5   20   12.1    2   1.2
      3  109.7   30   18.3    3    1.8       3	108.8   30   18.1    3   1.8
      4  146.3   40   24.4    4    2.4       4	145.1   40   24.2    4   2.4
      5  182.9   50   30.5    5    3.0       5	181.3   50   30.2    5   3.0
      6  219.5   60   36.6    6    3.7       6	217.6   60   36.3    6   3.6
      7  256.1                7    4.3       7	253.8                7   4.2
      8  292.7                8    4.9       8	290.1                8   4.8
      9  329.2                9    5.5       9	326.4                9   5.4
     10    5.8               10    6.1      10    2.6               10   6.0