HIGHLIGHTS
BEST TIME TO SEE: 20 January, around 19:00 UT for the Lunar X and V; 25 January, from 23:00 UT for the M35 occultation
The Moon is a popular target for January; a bright, easy to locate object if you have been lucky enough to receive a new telescope for Christmas. It’s also a popular photographic target, easily bright enough to register on the continually evolving imaging technology found within modern smartphones.
The Moon isn’t appreciated by everyone and for hunters of the more diffuse objects in the night sky – objects such as nebulae, comets and galaxies – it’s regarded as a bit of nuisance. This is especially true at this time of year, because the larger, brighter and generally more intrusive phases of the Moon ride higher in the sky.
Despite its apparent brilliance, the Moon has a relatively low reflectivity or albedo. Its surface reflects just 12 per cent of incoming light, equivalent to the reflectance of dull asphalt! Just imagine how bright it would appear if it had a significantly higher albedo.
If you can forgive the Moon its glare, there’s plenty to see on its surface, something we cover in detail every month in our ‘Moonwatch’ section (see page 52).
In addition, transient events such as occultations sometimes take place.
A great example occurs on 25 January when the Moon appears to move in front of the southern two-thirds of the open cluster M35 in Gemini, an event we’ve reported on over recent months too.
The 25 January event is particularly well-placed and suits viewing with a small telescope at low power.
The Moon will start to cover the cluster’s stars from 23:00 UT and with ▲ magnification this should be fairly easy to see as long as the sky is fairly transparent. It’s the dark, leading edge of a 91%-lit waxing gibbous Moon which leads the occultation and this will make things a little easier. The event draws to a close around 01:00 UT on 26 January.
Other popular events requiring a bit of luck with timing are so-called clairobscur effects. These occur when the Sun is in a particular position relative to a certain feature on the Moon’s surface. The way the feature’s shadows appear can cause a visual effect that makes the scene resemble something familiar. Two famous effects are known as the Lunar X and V. Here, the letters ‘X’ and ‘V’ appear on the Moon’s terminator, the dividing line between lunar day and night. The effects can be seen on the evening of
20 January, reaching peak visibility around 19:00 UT. Roughly speaking, the Lunar X will appear a quarter of the way up the Moon’s terminator from the southern point, the V appearing roughly at the terminator’s mid-point.