Lunar Observing - Earthshine

Another certificate offered by the Royal Astronomical Society of Canada is the Isabel Williamson Lunar Observing Certificate.  Isabel Williamson (1907-2000) was an active member of the Montreal Centre and instituted observing programs; the first of their kind in North America.  It is a fitting memorial that the Lunar Observing program is named after her.  In the 60's she would give each member a single sheet of paper with 325 lunar features named and marked and assigned everyone to find and record each of them.

The program requires an enormous amount of work.  There are 140 main categories each with several required observations and a few challenge observations.  Following the main categories is a libration challenge with 12 difficult observations that can only be done at certain times of the year.  The final section is an optional activity to find craters with Canadian connections.  The more than 50 page observing manual and relevant documents are given as a link below.

https://www.rasc.ca/isabel-williamson-lunar-observing-program

It is helpful to have a Moon Atlas to complete most of these objectives.  I use the Atlas of the Moon by Antonin Rukl.  It is out of print and a new copy can put you back up to $1000.  However, if you scour the internet and have key connections in other countries you can swing a used copy for as little as $20.  It is a beautifully illustrated atlas that will be a lifetime reference book for any lunar observation.  You can also access Rukl's maps online at the following location:

http://www.refractorland.org/HMA/Moon_Map.htm

In the observing program the second of hundreds of required observations is Earthshine.  The manual describes it as the following:

"Observe Earthshine on a waxing or waning crescent Moon.  Earthshine is a faint but noticeable glow on the unlit portion of the lunar disc that is caused by sunlight reflecting off the surface of the Earth back to the Moon.  The glow is most prominent during the early or late crescent phases, when from the lunar surface a nearly 'full Earth' is in view that reflets a significant amount of sunlight back to the Moon."

If you have ever observed a slim crescent Moon you may have noticed you can see the whole Moon, except it is dark.  On January 29, 2017 I had the opportunity to take a picture of this phenomenon.

Earthshine

If a person was standing on the Moon they would see the Earth as a large waning gibbous disc reflecting an enormous amount of light.