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Planetary Section, Bulletin No.7 - Part 2 -2- Naturally, colour filters are NOT to be used over the eyepiece. It is recanmended that the observer first sketch the major Martian surface on a prepared disk and, with pencil only, lightly shade in the darker areas. After a period of 20 minutes (to permit eye adaptation) he should then canpare the group of red-yellow reference strips, one by ore, with the general over-all appearance of Mars as seen in the telescope. Initially, this ocinparison might prove to be difficult, but with a little perseverance an observer will narrow his choice down to one strip and then, with further canpariscri, select One colour chip as being representative of the general colour of the Martian desert area. The observer would then take up the group of grey strips and, following the ssme procedure, would choose the closest colour match for the dark areas. He should then make note of the corresponding ntnnbers of the colours selected, to one side of the Mars drawing, The observer, having by now becane familiar with the use of the Colour Reference System, should then exanine a selected region on the Martian disk for subtle differences of colour, Such areas have been observed in the past on both the light and dark regions of Mars. When localized colour variations are observed, an outline depicting the boundaries and extent of such colour change should be noted on the drawing and the code number for this colour lettered directly on the drawing. Should this area be too small to superimpose the code number, simply use an arrow to identify it. An example of a hypothetical Mars drawing is presented below to aid the observer in the proper use of the Colour Reference System. (Mars diagram here.) Archie L. Ostrander, National Co-ordinator, Planetary Section, STANDING COMMITTEE ON OBSERVATIONAL ACTIVITIES 75 Rabbit Lane, 29 March, 1967. Islington, Ontario.