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.
Mississippi Mills Moon Click on this link to see the computed times for moonrise/moonset
Last Quarter (well a bit after)
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 (http://tech.groups.yahoo.com/group/OAFs))
“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.
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:
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 http://www.rasc.ca/observing/williamson-lunar-observing-certificate…
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.