Because the sky was steady, multiple exposures could be combined with Photoshop. The photograph above (455X, 7 inch Maksutov telescope, 6mm orthoscopic eyepiece, 1/15 & 1/30 second) is a combination of a slight overexposure with one given only half as much light. The composite is composed of 60% of the higher exposure with 40% of the fainter image. This procedure emphasized the dark detail on the face of the planet by lightening the bright areas while leaving the dark areas almost unchanged.
The picture below is another composite. The brighter image was subtracted from the dimmer image. Black and white both turned white, all midtones were compressed while the contrast scale of bright (but not white) areas was expanded. This brought out the detail inside the polar ice cap.
The broken ice area, surrounding the pure white ice in the center of the the southern ice cap is shown as a large dark area. The cap is primarily dry ice, that is solid carbon dioxide, which sublimates at -159°C at the atmospheric pressure of Mars which is about 1% that of earth's air pressure. [from the CRC Handbook of Chemistry and Physics]
The tundra then, is around -160°C, but I don't know what accounts for the sharp outer edge of the ice cap, does it indicate a sharp temperature gradient? I'd like to find independent confirmation of 1) the shape and extent of the tundra, 2) its composition and 3) it's temperature.
Mars is still here.
Mars at 312X - Schwaar scope with a 4.8 Nagler / 2X barlow
And the seeing is pretty steady, as this drawing done over a twenty minute period just prior to midnight, indicates. The distinct, Africa shaped area in the center of the planet is Margaritifer, with light areas Xanthe to the west (right) and Arabia to the north-east.
It's time to get the Mak-7 out and shoot this thing at high mag.
