670315Planetary7a_p1

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                       THE ROYAL ASTRONOMICAL SOCIETY OF CANADA

                                                                        Bulletin No. 7

                                   PLANETARY SECTION

MARS

As Canada's 100th birthday is also the year for one of the more favourable apparitions of
Mars, the National Co-ordinator suggests that a 1967 map of Mars should be prepared by
this Section as our Centennial contribution. A project of this magnitude requires the
active participation of observers from afl Centres of the Society to ensure its success.

The red planet will be nearest the earth on April 21-22, an ideal time for comfortable
observing. Observations should cover the months of March, April and May with a concerted
effort between March 23 and May 23. Since the period of rotation of Mars is 40 minutes
longer than that of the earth, at the sane tine an observer win look directly at a given
area on Mars 40 minutes later than on the previous night. Consequently, arty Martian
feature can be viewed on successive nights at a different local time, with new areas caning
into view. After forty days, both hemispheres will have been observed fran any one
location. The advantage of having participants observe and record from various locations
across Canada is readily apparent. With the time zones covering 5½ hours on the same
evening, an observer in Halifax and an observer in Vancouver (at 6:00 p.m. local time)
will see totally different regions of Mars (displaced some 75°).

COLOUR MAP:

With the co-operation of members of Centres of the R.A.S.C., this Section will attempt to
produce this map in an accurate colour representation. For the serious participant, a
selection of 77 colour chips has been obtained, 35 hues of colours which might appear on
the ocher "desert" maria, and 4+2 shades for the dark "continental" regions. These are
numbered and mounted on cardboard strips and packaged for convenient comparison with the
colour of the Martian disk observed at the eyepiece.

The observer should select from the strip the colour approximating that viewed and write
the number on the particular region on his drawing. For these comparisons a clear white
tungsten light should be used without colour filters. A complete set of colour stripe
will be sent to each Centre shortly with special instructions. A limited supply of
additional sets is available.

OBSERVING HINTS:

After a first telescopic glimpse of Mars, a beginner may feel that this small pinkish disk
is featureless except for the bright white areas at the poles. However, continuous
observing of the planet for at least 20 minutes permits the eye to detect contrasts of
shade and colour. Only then will the observer see the fine detail which is so apparent
to one with experience.

Sketching is a valuable aid in training the eye to detect all there is to see. The
observer then subconsciously scrutinizes small areas of the disk to enable these to be
recorded. This type of search makes one fully aware of the abundance of detail that can
be resolved. A red filter (Kodak Wratten 25) used at the eyepiece helps in discerning
the greys from the reds.

At the eyepiece of an inverting telescope, the observer will notice that the Martian fea-
tures first appear on the right limb, move from right to left (Martian west to east) across
the central meridian of the disk and disappear on the left limb. As this motion is rapid,
all drawings or sketches should be completed in as short a time as possible (5-10 minutes);
the accuracy of the central meridian notations should be to the nearest minute.

Sample report forms are enclosed; please request additional copies.