Alphonsus and Flammarion

[Mike JW]

This the third sketch from my outing  on Jan 3rd. 

I have looked at Alphonsus many times and with its companions Ptolemaeus and Arzachel makes for a wonderful sight. Alphonsus is about 118km in diameter. Its messed up walls rise to 2700m or thereabouts. To me the crater has a hint of being hexagonal. It has a lone central peak which rises to 1.5km and sits on a ridge of material. This ridge is possibly ejecta material from the Imbrium impact. Some folk in the past thought the central peak might have been volcanic but latest evidence suggests it is not – I assume it is a rebound structure after the original impact. Some of the crater walls have linear valleys (troughs) which point to Mare Imbrium and thus are likely to be due to flying chunks of rocks hurtling through the crater walls – what a sight that must been. Until this particular sketch I had not registered the dark areas in the crater floor. They are pyroclastic deposits from volcanoes in the crater although some folk suggest they are due to impacts bringing up dark material from below. However close up images show volcanic vents in the area. Rilles are also found in the areas of these dark spots.

Not far away was Crater Flammarion. I am not sure I have bothered to have a proper look at this impact crater.It is 75km across with a fairly smooth flat floor. On this occasion the freaky crater shadows on the East were just jaw dropping, so a sketch had to be created. The black, deep crater at the top is Mosting and from its shadow it must have two higher peaks as indicated by the pointy shadows at the north and south end of its shadow. I always enjoy "spot the peaks" - the next ridge down has one peak, the next one south has 3 and in decreasing height? I wonder what the real situation is? As I played this game I suddenly noticed there was a funny line on the northern end of Crater F. Close inspection revealed Rima Flammarion ( a new one to me). Images show it extending out of the crater to the east. Amazingly so its line coincides exactly with the edge of the big triangle shadow so no chance for me to spot its Eastward journey.

Two different fonts in this posting as I copied and pasted the first paragraph from my records.

Mike

Edited January 7, 2020 by Mike JW

[Fraunhoffer]

I love this technique.
I got some sketching pencils and charcoals for Christmas. Eager to try them out.

 

[Mike JW]

I tend to use sketching pencils - 2B, 4B, 6B, For black I have been trying out Indian Ink and a small artist brush (needs two coats). For white I use gel pens. Charcoal makes such a mess. I find carbon pencils are good for the black shadows. All my sketches are roughed out at the eyepiece and then done indoors. No way could I do them at the eyepiece.

Looking forward to your pencil sketches.

Mike