Lunar Occultation of Mars, 8th December 2022

Just to quickly recap what it was I was hoping to see, an occultation is when a celestial body moves in front of another one, as seen from a particular place on Earth, and blocks the observer's view of the "background" object. Occultations of one planet by another are exceedingly rare but those involving the Moon are more frequent as the apparent size of the Moon is much greater than that of any other celestial object (apart from the Sun, of course). Even so, in the case of Mars there has not been even a near-miss lunar occultation visible from my part of the UK since the last one in 2007 and there will not be another near or actual occultation this side of 2040! I was thus very keen to observe this one.

The severe downside to this potential observation was that it would take place from 5am to 6am on what promised to be a very cold dawn if skies were clear. I thus laid out two pairs of trousers, three nice warm inner layers plus a thick jumper and a fleece, a woolly hat, and two pairs of gloves - fingerless for when I was taking pictures and a "thinsulate" pair for when I was waiting for things to happen! I didn't want to be setting up my equipment with frost on the ground so I aligned my equatorial mount the day before (to view the section of the sky indicated by the Moon's azimuth that morning, conveniently lying nicely between the two houses across the road!) and marked the positions of the legs before bringing it back indoors again and retiring to bed.

The alarm going off at 4:30am was rather a shock but having crawled out of bed a quick look at the sky indicated that I might be in luck. I thus pulled on all my warm clothing and ventured out - while apologising to our eldest cat for so rudely waking him up! Mars was already so close to the Moon that it was not easily visible by eye, but once everything was set up again and "tweaked" a little the view through my camera confirmed that all was well. I thus took a few early shots and then waited for the predicted time of ingress to come near before firing off many more, at two exposures which I had determined from the early shots should give usable results. I had been concerned that I would not be able to capture both Mars and the Moon at the same exposure without under-exposing Mars or over-exposing the Moon but in practice this was not a problem - helped, no doubt, by the fact that Mars was close to opposition and thus at its brightest for the year.

Once it was clear that Mars had disappeared I brought my equipment back indoors again and retired to bed for a short period of rest & warming. The Moon takes about an hour to move across the sky by its own diameter relative to the stars and so, because this occultation was very nearly "central" i.e. the track of Mars behind the Moon passed very close to the Moon's centre, Mars would be occulted for nearly an hour - no point in staying outside for that long with nothing to look at!

Having again been awakened by my alarm, I was pleased to see that the sky was still clear so I dressed warmly, exited, and set everything up again to await the predicted time of egress. I could not risk missing this, so started picture taking well beforehand and continued until Mars was some distance away from the Moon's limb. I then breathed a deep sigh of relief, took everything back indoors, and fell into bed once again hoping I had captured a good set of images.

But had I? Click the links below to find out.

  Pictures of the occultation        Technical Info

  Animations of the occultation