2014 January 19, 17.84-day Moon

It’s fun to sketch lunar phases, especially when the weather allows you to record several nights during a lunation. There are a few tips I can offer that may be helpful if you’ve not yet tried your hand at it.

First of all, it can be easier to sketch highlights rather than shadows, especially when time is of the essence while sketching along the terminator. To do this, try using white pastel pencils on black paper. Concentrate on the brightest areas. The shadows will automatically form before your eyes. Next, it’s important to begin a full-phase lunar sketch along the terminator, as that’s where you’ll notice the most shadow change. During the first half of lunation (waxing phase), more lunar terrain becomes visible during the course of your observation as the light encroaches on the shadows. Shadows move inward, swallowing up visible terrain during the second half of a lunation, termed waning. To finish the sketch, add prominent lunar features to be used as anchors. They will aid in accurate placements and proportions for the remainder of the sketch.

I’ve indicated the favorable libration with an arrow toward the top of the sketch. Libration is the slow wobbling motion of the Moon as viewed from Earth. Over time, libration in longitude and latitude allows us to observe about 59% more of the Moon’s surface as it wobbles back and forth. The indicated libration on the sketch means that more lunar terrain is visible where the arrow is pointed. This also means that less lunar terrain is visible along the terminator on the opposite side of the sketch.

2014 01 19, 0430-0900 UT (-6) 17.84-day Moon
Erika Rix, Texas, http://www.pcwobservatory.com
102mm f/9.8 refractor, LXD75, 20mm, 50x, 13%T Moon filter
30F, 48% H, c/c, Antoniadi II, Transparency 4/6
Colongitude: 127.9°
Phase: 326.3°
Lunation: 17.84 days
Illumination: 91.6%

Eyepiece sketch on black Strathmore Artagain paper, white Conte crayon, white charcoal pencil, black Derwent charcoal pencil, black woodless oil pencil, blending stump.