2012 10 04 – Hercules and Atlas | PCW Memorial Observatory

2012 10 04 – Hercules and Atlas

2012 10 04, 0500 UT – 0636 UT Hercules and Atlas
Erika Rix, Texas – http://www.pcwobservatory.com

AT6RC f/9 1370mm, LXD75, Baader Planetarium Hyperion 8-24mm Mark III (FOV 68 degrees at 171x), no filter
69F, 70% H, light breeze, lightly scattered, Antoniadi III, T 4/6
Alt: 31deg 14´, Az: 84deg 58´ to Alt: 51deg 28´, Az: 97deg 02´
Phase: 314.8 degrees, Lunation: 18.12 d, Illumination: 85.2%
Lib. Lat: +00:26, Lib. Long: +00.35

Hercules
Type: crater
Geological period: Eratosthenian (From -3.2 billion years to -1.1 billion years)
Dimension: 71km
Height: ~3000 meters
Steep slopes to west, terraced walls to east. Flat floor with hills and crater E.

Atlas
Type: crater
Geological period: Upper Imbrian (From -3.8 billion years to -3.2 billion years)
Dimension: 90km
Height: ~2800 meters
Steep slopes, central mountain, rugged floor, terraced walls.

Eyepiece sketch on black Strathmore Artagain paper, white Conte’ crayon and pencil, black oil pencil.

It’s really fun to race against time while sketching along the terminator during the waning gibbous phase. I sound like a broken record stating that it’s much easier when sketching in the highlights on black paper instead of the shadows on white while working along the terminator, especially when the feature can be swallowed up by shadow.

My first sketch of this pair of craters was in 2005.

Atlas and Hercules – 2005 02 27

It was one of my first astronomical sketches and I struggled to record the observation as accurately as I could – just like I do today. It was with the support of other lunar sketchers on the Cloudy Nights Telescope Reviews forum that gave me the confidence to pursue this faucet of astronomy.

Working out the eyepiece combo with the magnification, the 2005 sketch was done with the ETX70AT. The two observations are nearly the same with regards to lunation and time of night plus altitude and azimuth figures. The big exception is in libration.

2012 10 04: Lib. Lat: +00:26, Lib. Long: +00.35
2005 02 27: Lib. Lat: -00:50, Lib. Long: -05.04

This is a very good example how libration affects the view we see on the Moon. As a side note to help put things into perspective of what you can expect to see through a telescope at 171x magnification, crater Hercules H is 7km wide.

Reference material:
Rukl 14 and 15
Wood, C., The Modern Moon: A Personal View, Sky Publishing Corporation, Cambridge, MA 2003, pg 72
Lunar Orbiter Photo of Atlas and Hercules region

Labelled version: