My night with the 6 inch on 10th Dec 05

 Peter Parish  

Around 15.00 GMT while it was still light I set up the MKAS fl2.6 6 inch refractor in my back garden. Seeing promised to be good and I was not disappointed. I had a look at Mars with the usual 9m/m eyepiece giving a power of x 214. The phase is now obvious. At 18h 07m, kneeling behind the telescope on my bit of carpet remnant I did a drawing see below. Mare Sirenum was much the most prominent dark marking stretching like a giant tadpole horizontally from the terminator to near the middle of the planet. There was an off white patch just above it (South) but this was not as white as the NPH (North Polar Hood) clearly visible on the North limb below or the White cloud line extending along the western limb. The most elusive feature which I could only see for certain in an Orange 21 filter was the thin line like shading extending South and west from the western end of Mare Sirenum (the tadpoles head).

On the 9th December I'd observed Mars at Central Meridian (CM) longitude 224.2 degrees and I could not see the SPC (South Polar Cap) but to my surprise I could see it now. Although it was a very small white dot, it was unmistakeable. The CM longitude was 121.2 degrees. Richard McKim, the BAA Mars section director and a leading authority on Mars, told me the SPC was asymmetrical which is off to the side of Mars's South polar axis and best seen near the longitude of Argyre (CM 20 to 40 degrees). My observation of the 9th was almost 180 degrees away from there but on the 10th (see drawing blow) it was under 85 degrees away. From a planetary viewpoint I enjoyed seeing that improved to Antoniadi 2, a view approaching the telescopes optical potential. Atmospheric steadiness is always paramount for the planets.

With the naked eye Mars still appears like a very bright reddish brown star shining unwaveringly in the constellation of Aries. On the 10th the planet was magnitude —1.2 and still far outshining the other surrounding winter stars such as Hamal magnitude +2.0 and Sheraton magnitude +2.6, the principle stars in the host constellation Aries. Even the brightest nearby star, Capella in Auriga magnitude +0.08 looked dim by comparison. Only Sirius exactly equalled its brilliance, indeed the star's white colour emphasized Mars's redness. The planet is still conspicuous but its brightness is reducing. By the end of December 2005, its magnitude will have dropped to about — 0.6