Sketched September 10, 2003 from the our downtown San Rafael public observing session in Marin county, CA at midnight pacific DST (daylight savings time) or 07:00 UT September 11. Seeing excellent, transparency LM 3.0, full moon and streetlights nearby. We also showed Mars and moon to 100 people on the sidewalk during a 3 hour sidewalk astronomy session.
|Date: 09/11/03 Lat 37N, Long 122W, elev. 200 feet||Sketch Time (UT): 7:00, (local time): midnight DST|
|Central Meridian: 307°||Filters: none|
|Instruments: 12.5-inch f/5.75 Litebox traveldob reflector, plus f/9 AP180EDT refractor.||Distance from earth 0.39 AU, 58.5m km, 36.3m miles|
|Magnification: (9mm) 202x and (10mm's) 160x Radian+barlow in AP180EDT for this sketch||Transp. 3/6, Seeing 10/10, Antoniadi (I-V): I|
|Apparent Size: 24.01"||Magnitude: -2.7|
Details about the sketch: I used my f/5.75 12.5-inch Litebox reflector, 9 Nagler for 202x plus our f/9 AP180EDT refractor, binoviewer and both 10mm Radian (160x) and binoviewer, Barcon barlow and 16mm ZAO eyepieces (300X) for this sketch. Sketched on the sidewalk plaza in town under the glow of streetlights, and in-between eyepiece viewers who wanted a look at Mars.
Details about Mars: Diameter 24.01 arc seconds (Jupiter is about 30 -50 arc seconds in diameter depending on its distance from earth). Central Meridian 307 - the imaginary line passing through the planetary poles of rotation and bisecting the planetary disk, and is used to determine the longitude during an observing session.
The terminator....is BACK! No, not THAT terminator, but where daylight ends and evening begins on Mars. The terminator is now on the right and the planet is rotating left to right. In my sketches, the planet rotates Martian east to Martian west to match most other images and sketches. The features rotate from left to right, but due to a stroboscopic effect - earth and Mars' rotations are different by less than an hour each day so it actually seems like the features are rotating on the opposite direction. It is just like if a tire wheel is rotating just a little slower than the frame rate in which you are taking a picture and it appears to rotate backwards because the wheel will not quite be making a full rotation for each snap shot. So if you look at Mars at exactly the same time each night, it will appear to rotate backwards. Anyway, now the terminator is on the other side of the disk as we have passed opposition and Mars' phase is 99%.
Syrtis Major is the prominent angular feature pointing toward the north pole of the planet. To the left (east) is a lighter area called Syria. Between Syrtis Major and the shrinking south polar cap is the large oval impact crater basin called Hellas. The basin of Hellas showed evidence of another dust storm to me last night. Parts of the basin (the more southerly section closest to the ice cap) appeared darker than the more northerly area closer to Syrtis Major which appeared lighter. In the course of an hour of an observing session, the dust is not capable of shifting accross an area larger than the USA. But people have reported seeing changes in this area occurring in under an hour. I personally think it is the atmospheric seeing conditions that are changin', rather than a mighty wind blowin', blowin' dust on Mars (in an hour, I mean). To me the shape of Hellas - usually more oval, was more round during this observing session. Frequent observations will tell us if another big dust storm is brewing.
White Oaks Home | Sketches Index | Mars 2003 Index | Back | Next