maria – Page 13 – Astronomy Sketch of the Day

Between Serenity and Tranquility

Craters Plinius and Dawes

After more than 23 days of very cold, cloudy, winter weather an approaching warm front got me out under the moon and stars on this clear, transparent night of good seeing. I centered the telescope field of view on craters Plinius and Dawes near the lunar terminator. This is the region I selected for my sketching. Plinius is the largest (43km) crater in the sketch. Its central peak and irregular, cratered floor are hidden in darkness but a hint of its terraced walls can be seen on the illuminated inner west margin. Further to the west the peaks near Promontorium Archeruia are catching the rising sunrays. About 55 km to the south of Plinius is crater Ross, a 26 km diameter crater identified only by its sunlit rim. This crater rests in the Sea of Tranquility. To the northeast of Plinius near the edge of the Sea of Serenity is the 19 km crater Dawes, its floor mostly in shadow. Directly to the north of Plinius the rilles of Plinius were clearly visible. In addition a small part of Dorsum Nicol is also seen. All of these features are positioned on the dark colored lavas at the boundary between the two above mentioned seas. The grazing sunlight helped to enhance the changes in topography.

Frank McCabe

Sketch details:
For this sketch I used: black Strathmore 400 Artagain paper 9”x12”, white and
black Conte’ pastel pencils and a soft leather blending stump.
Telescope: 10 inch f/ 5.7 Dobsonian and 6 mm eyepiece
Date: 2-23-2007 1:05-1:45 UT
Temperature: 0C ( 32F)
Clear, calm
Seeing: Antoniadi II
Colongitude 339 degrees
Lunation 5.4 days
Illumination 35.7%

Entrance to a frozen Hell

There was a very thick mist that night, and the moon was hardly visible behind the clouds. I put the scope outside with no intent for observing, as I wanted to adjust a new home made focuser. It was a very pleasing surprise to discover that there was absolutely no turbulence at all on the Moon.
Despite the thick clouds, the light and contrasts were still strong, and everything was frozen, no movement at all. I jumped on my pencils, and made a draft of Eratosthenes, one of my favorite craters on the Moon, maybe my favorite. I like the long and thin design of the Apennine mountains terminating like a lyra, with that black and strange hole, just at the limit of infinite darkness.

Pierre Desvaux

– Medium used: White Conté on black Canson paper
– Telescope: Home made 16″ Dobson, Nagler 12, barlow 2X Celestron
– Date: December 2006
– Place: Blanzy, Bourgogne, France

The shepard philosopher

When I looked outside that Sunday evening there was not a cloud in the sky and the eight day moon was shining down on me from a very favourable angle. There were far too many desirable sketches available, and my eyes darted from Rupes Recta toward the south, to Eratosthens and the shadows and highlands spinning off it, and further north to Plato sitting on the darkness of the terminator. It was a difficult choice, but I settled on Plato just because it had slightly more interesting shadows and also some very bright highlights emerging from the darkness near its northern rim. A long thin pointed shadow poured from the base of Mons Pico toward the terminator and also from another high area to its right as I viewed it. These shadows lengthening in the hour it took to do this sketch. Just above Mons Pico as I viewed (south is up) a change in the lunar surface was apparent in the form of an Eiffel tower shaped greyness which swept up to and finished at Piazzi Smith. Mons Piton sits with Piazzi in area across from Montes Alpes which had several sun kissed high points. I observed the needle like Vallis Alpes cutting a sharp gash in the surface through rugged lunar land, lit slightly on its northern edge. Feathery shadows set of the shape of Plato and detached from its northern rim, very bright high areas warmed themselves as they became uncloaked from the blackness.

Deirdre Kelleghan
President
Irish Astronomical Society 1937 – 2007

Sketch details:

February 25th 2007
20:45UT – 21:45UT
53.2000ºN, 6.1000º W
200mm/F6/6.3mm Plossel/193X
8.19 days
Seeing 2
Trans Average
300gm Daler R paper/DR soft pastels/Black watercolour pencil/wooden toothpick
www.irishastrosoc.org

Plato and Sheep

Nestled on the plains between Mare Imbrium and Mare Frigoris lies the nearly lava filled crater Plato. This 100 km, dark pool of frozen lava has a darker tone than the lava that filled the Imbrium basin. Crater counts indicate that the lavas that filled Plato are actually younger than the Mare lavas of Imbrium. The history of emplacement goes something like this: the Imbrium basin was created first, followed by the impact that created Plato, and then the gradual fill in of basaltic lava that flooded Imbrium and much of the existing basin rings and superposed craters. This left untouched some of the isolated massifs that are now known as Plato’s Sheep, including the towering Montes Pico (2500 meters high), Piton (2000 meters high), and the Tenneriffe Mountains (2500 meters high). Finally came the slow lava inundation of Plato itself. Above Plato and rendered with wonderful precision is the Vallis Alpes, a large graben (extension) fault which probably formed as a result of the original impact that created Imbrium. Dee’s beautiful sketch clearly depicts the drama that awaits the observer when the telescope is turned to this region as the terminator passes through.