Six Degrees of Libration

Lunar Crater Barrow
Sketch and Details by Frank McCabe

With six and one half degrees of libration in latitude, the lunar North Polar Region was favorably positioned for viewing from our home planet. A morning sun ray was illuminating the floor of crater Barrow as I set up my scope for an evening of observing the moon and stars. I was not expecting to sketch the moon tonight because of its low altitude. I just couldn’t pass up this opportunity to catch this sight on the floor of Barrow and a sketch was in order.

Crater Barrow is an old worn 95 km. Nectarian period impact dent adjacent to larger older walled plain crater Meton (126 km.). Meton appears particularly large and irregular in shape because of the common lava flooded floors of Meton, C, D E, and F. Much smaller and younger crater B (6 km.) can be seen on the floor of Meton C (77 km.). It was only after I began sketching that I noticed a second ray of sunlight crossing the floor of Scoresby M (54 km.) just to the north of Barrow. Other craters visibly here include: Scoresby (57 km.) one of the younger craters here with the brightly lit rim and just northeast of M, Challis (56 km.) and Main (48 km.) are paired up to the north of M.

Part way through the sketching process I needed to move the entire setup because I lost the moon to a large maple tree. This was a most rewarding observing session even with a moon that tried to hide from my vantage point.

Sketching:

For this sketch I used: black Strathmore 400 Artagain paper 12”x14”, white and black Conte’ pastel pencils and a blending stump. After scanning, Brightness was slightly decreased (-4) and contrast increased (+4) using Microsoft Office Picture Manager.

Telescope: 10 inch f/ 5.7 Dobsonian and 6 mm eyepiece 241 x

Date: 7-10-2008, 1:45-2:50 UT

Temperature: 22° C (72° F)

Partly Cloudy, calm

Seeing: Antoniadi III

Colongitude 353.1 °

Libration in Latitude: 6° 30’

Lunation 7 days

Illumination 49.2 %

Frank McCabe