Too Cold? Try lunar observing…


During a stretch of -20 deg nights, many avid amateur astronomers cower in a warm house.  But some learn how  to cheerfully saunter outdoors for a brief look at.. the moon. Pre-planning a lunar observing session  simplifies the problem of deciding where to look, and what you should use to observe.  When the weather makes it difficult to observe (extreme cold, extremely annoying mosquitoes, etc), we tend to lose connection with the night sky and the current  phase of the moon .

When to do Lunar Observing

To plan a lunar observing session, you need to know the current phase of the moon and the time of moonrise or moonset. It is particularly good to know  within the month what nights are on the first and last ‘quarter’ lunar  period. Every month there are 4 quarters, and the first and last quarters of the moon phase  show the best mountain, crater and dome features on the moon. Why?  –  because a well-defined terminator or shadow line  not only picks out the lunar day side from the night side, but also brings out low relief features due to the casting of shadows.  So amateur astronomers like to have a calender that shows the moon phase, and the time of moonrise/moonset;  to hunt down features more plainly ‘lowlighted’  in the first and last quarter.

Each months lunar phase is available here:
Mississippi Mills Moon    Click on this link to see the computed times for moonrise/moonset


Last Quarter (well a bit after)


New Moon

First Quarter

Full Moon

Reproduced from SkyWays: Astronomy Handbook for Teachers by Mary Lou Whitehorne,
used with permission from The Royal Astronomical Society of Canada (RASC).

The above exercise shows the shadow geometry for all four moon quarters.   Note that shadows on the moon  make it much easier to pick out lunar features.  These shadows occur  when the moon is  less than fully illuminated, seen as percent illumination on the calendar: The more the % illumination, the flatter the features look.

For these features and more, one of the best ways to make a project study out of the moon is to observe with the Royal Astronomical Society of Canada’s (RASC) Isabel Williamson Lunar guide.  Shadows reveal so much… including the presence of low-relief domes which are not the result of impacts on the moon but rather volcanic action on the moon. That would be the last time there was volcanic action on the moon (say 1 billion years ago).  As noted, in the Lunar Guide:  ” As the Moon cooled after its formation volcanic activity slowed down and eventually ceased about one billion years ago. Volcanic domes are rare and interesting targets.”  This is the guidebook we use to work on the RASC Lunar Certificate program.

Rick Wagner, an avid amateur observer wrote in the Ottawa Astronomy FriendS group (

“It’s [ the Lunar Certificate program] is one of the  more substantial certificate programs they have with many many objects  included, plus things like seeing and recording all the various phases,  libration challenges, very new or very old (24hr from new) moons, observation with the naked eye, binoculars and telescope. It has a  couple of basic drawing forms included.  It also starts off with a  description of lunar history, features etc..   I think once I’ve finished the  program I’ll know virtually every feature on the Moon.”

In fact, it may have helped him identify one of the mystery images Mike Wirth’s posted.  At Equulus South Observatory, Mike studies lunar features, and is currently on a dome quest. Here are some images of dome features. They look like mosquito bites because of the low relief just 100s of meters, and the scabby craterlet on top.

Courtesy Mike Wirths ca 2009
Click to enlarge image and see the names of the domes.


Massimo Cicognani drawing carried out on 18 august 2000 at 22:30 UTDomes Cauchy omega and Tau . Click to enlarge.











Compare Mike’s image with the drawing by Massima Ciognani to understand the dome structures.

Mike has a montage of recent images which include lunar features such as craters, mountains, rilles and domes:


Courtesy Mike Wirths
Equulus South Observatory



If you would like to get started on a lunar observing project  start  with Williamson Lunar Guide. And once you go through the guide, using the   Lunar Observing Forms you can earn a certificate from the Royal Astronomical Society of Canada shown here:  RASC  Lunar Observing Certificate. (You will need to join the RASC to apply for the certificate).

For more information on the lunar observing program and the RASC Lunar Certificate, visit

For the next week or so,  the moon will rise in the early morning hours, a good excuse to stay  underneath a pile of blankets and prepare your next quick saunter outdoors for a moonlight session.