Sunday, December 16, 2007

Trapezium & Mars form Central Park

Session name:20071208.1945

On this short session, Kin and I observed and shared the views of Mars to about a dozen pedestrians and dog owners. Most of the evening the sky background appeared bright to our south and up to zenith, a little haze seemed to fill the air diffusing the lights of CitiGroup building and Times Square. We commented that seeing was not so good and transparency was significantly better in the celestial northeast with a naked eye limiting magnitude around magnitude 5.0.

At magnification to 121x, I could resolve the E & F star of the Trapezium. (Stan was able to see them and I can't recall if Kin separate them.) Below are two diagrams I created for use on the Palm. One is based on information in Burnham's Handbook for the reflector where it is inverted and mirror reversed. The Garfinkle-based diagram has north at top and adds a few extra measurements to stars beyond the reach of this 4" in city skies.

What makes resolving the magnitude 11 E & F stars challenging is the brightness of the nearby A & C stars, respectively. My experience has been that the E star is easier to detect than the F star because of A's brightness.

Trapezium Chart - BurnhamTrapezium Chart - Burnham

Trapezium Chart - GarfinkleTrapezium Chart - Garfinkle

Mars sketchWe could see surface features in the northern hemisphere with a white polar cap and contrasting maria: Mare Boreum formed a collar around the bright cap with Mare Acidalium adding some area in the center. In the southern hemisphere a large, dark smudgy area contrasted with the brightening around the limb and across the equatorial zone. It was difficult discern shape and extent since contrast was low with the surrounding surface. I suspect a great part of the darker albedo was Mare Erythraeum.

Most of the pedestrians were able to see the darker collar and obviously contrasting northern polar cap. I don't think they had as easy a time with the southern hemisphere or equatorial zone.

We disagreed on what we sensed across the equatorial region. Kin saw a brigher area extending across the entire disk, describing it as a contrast with the maria to north and south. I said I saw a crisp white disc that stood out above that bright equatorial band. The white spot is Chryse Planitia. I made this remark after consulting Brian Tung's terrific Palm application, Mars Map.
I felt that I saw it but lost confidence and considered that averted imagination miught be at play. That is why the sketch shows dots along the central region and doesn't include a small pea shape just east of center (opposite direction of drift).

Burnham's Celestial Handbook: An Observer's Guide to the Universe
Robert Burnham, Jr.

Star-Hopping: Your Visa to Viewing the Universe
Robert Garfinkle

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