Promontorium Laplace

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Observation Notes:
Promontorium Laplace was in a very striking position along the terminator when I made this observation Monday night. The gusting breezes tried to shake me off, testing my patience with the vibrating image in the eyepiece, but I hung in long enough to attempt to capture the majesty of the sight. Just south of the sharp, concave arrowhead of Laplace, wrinkled ridges ran smoothly across the lava filled plains and swirled off to the south, marking the boundary between the twilight of Imbrium in the east and pitch black of Iridum to the west. The contrast between these smooth, flowing ridges and the rocky, sharp edges of the Promontory was very appealing. The crisp, dark circle of Laplace D anchored the angular north region, while white-lipped disk of Laplace A punctured the rippling ridges to the south. To the northwest, Maupertuis Crater simmered up through the deep shadows like the fossilized jaws of a great sea monster.

The experience of sketching this feature was unfortunately stressful. I know it should be relaxing, but the wind was driving me out of my mind. Wind does that to me in prolonged doses anyway, but at the eyepiece, it's an extra slice of grrr. There are so many blocky features and ridges in a view like this that I have a hard time finishing my rough outline before trying to jab in all the different crags and crevices. I find myself digging into tinier and tinier fractals of detail before stepping back (as the wind rattles the scope), and trying to convince myself to finish the rest of the rough outline.

'DISCIPLINE! You. Lack. DISCIPLINE! Never learn you will.'

I really stress myself out worrying over features I'm going to lose to sunrise or sunset on the terminator, is what the problem is. Sketches of objects further exposed sunlit regions are less worrisome, but also much less dramatic. I just need to figure out where I can pick up some chill-pills. I hope you've had a chance to dwell on this fantastic region recently.

Promontorium Laplace is the northeastern tip of the Jura Mountain range that cusps the bay of Sinus Iridum which itself is a northwestern extension to Mare Imbrium. These mountains rise as high as 6000 meters above the smooth floor of Iridum. Sinus Iridum is a 260 km diameter impact basin that has been filled with lava. The obscured remains of the southern wall of this basin can still be seen as wrinkle ridges visible in the sketch. Maupertuis Crater, buried in the heart of the promontory is 46 km in diameter.

SubjectPromontorium Laplace
Phase/Age9.5 days old
Size*50 km
Date/TimeSeptember 12, 2005, 8:30 - 10:00 PM MST (September 13, 2005, 03:30 - 05:00 UT)
Observing Loc.Flagstaff, AZ - Home
InstrumentOrion SVP 6LT Reflector (150 mm dia./1200 mm F/L)
Eyepieces/Mag.10 mm + 2X Barlow (240X)
ConditionsClear, breezy, 55°F
SeeingAnt. III
SourcesThe Moon Observer's Guide By Peter Grego
* Based on published data.

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This page contains a single entry by Jeremy Perez published on September 12, 2005 10:00 PM.

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