620401PlanetaryInstr1_p2

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General Instructions, p.2                                             Planetary Section


areas where Daylight Time is in effect, one hour less than the number given in the
Handbook should be added. The double date is not used here, the date changing at 0 U.T.

     Seeing. The steadiness of the telescopic image is usually recorded on a numerical
scale with 0 representing seeing so bad that no detail can be made out to 10 when the
image is absolutely steady for long periods of time (never achieved in practice!). On
most nights the seeing is around 3 or 4, and values above 6 are recorded very
infrequently

     Transparency This gives the clarity of the sicy and is usually taken as the
magnitude of the fairtest star visible with the naked eye at about the same altitude
as the planet.

     Central Meridian and "k". The central meridian of the planet at the time of
observation may be calculated for Mars and Jupiter from tables in the Handbook or the
American Ephemeris. Since Mars has many permanent surface features and a well-known
rotation period, longitudes are given in terms of an internationally agreed upon system.
the Ephemeris predicts. the meridian that will pass through the centre of the disk at 0h
U.T. each night, and from this it is possible to calculate the central meridian (or
"C.M.") for any other time. Because.Jupiter's surface is not visible, two arbitrary
longitude systems aS used as a reference: System I for regions between the middle of
the North Equatorial Belt and the middle of the South Equatorial Belt, and System II for
the rest of the planet. "k" is the fraction of the planetary disk which is illuminated
and is useful in comparing drawings of Mercury and Venus. It is tabulated in the
Ephemeris.

     Station. The location where the observation was made may not necessarily be the
same as the obsener's mailing address and so should be indicated here. 

     Drawing. A two-inch diameter circle should be drawn in this space with a pair of
compasses except for drawings of Jupiter and Saturn. For Jupiter, Form No 1-J with the
specially printed outline should be used. This outline has the correct shape for
Jupiter's slightly elliptical disk, and the planet should be drawn so that its belts are
parallel to the major tis of the ellipse. Since the aspect of Saturn's rings changes
continuously, no outline can be given For accurate drawing the dimensions of the disk
and ring system must be taken from the Ephemeris and suitable ellipses drawn. After a
drawing is completed, its appearance may be improved by carefully blacking in the
background with a felt-nibbed marking pen (such as the Carter's "Marks-a-Lot").

     Intensity Estimates: Another circle may be placed here for recording the
intensities of the features observed (see p3).

     Observer's Remarks. Any information that may be useful in interpreting the drawing
should be entered here. Most observers err on the side of making too remarks;
something that might not seem important at the time may take on a greater significance
when compared with other observations. Remarks may be continued on the back of the form
provided that nothing is written on the back of the drawing itself.

     All observations should be sent to your Centre's planetary chairman not less
frequently than once a month. If drawings are sent by mail, please do not fold the form
across the drawing.

MAKING A DRAWING

    The observer should equip himself with the following before going to the telescope:

    (a)  Some sort of dr&ing board to which the report form can be firmly attached
    (b)  A suitable penoil (my own preference is for the 2B lead) One with an eraser
         attached is a great convenience; otherwise
    (c)  A fairly soft eraser, perhaps sharpened to a point.
    (d)  An "artist's stump".  This is a small roll of blotting paper sharpened to a
         point (obtainable for a few cents from any art supply store) which is used to