Blistering basalt

Over the past several months detailed images of the Moon have been received from SPA members Anthony Ayiomamitis (Greece), Mike Brown, Alan Clitherow, John Dee, Dave Finnigan, Tony Ireland, Ernest Richardson, David Scanlan and Larry Todd (New Zealand). Lunar observational drawings have been received from Peter Grego, Philip Jennings and Graham Sparrow. Since I also receive many lunar images and observations in my capacity as Assistant Director to the BAA Lunar Section it’s sometimes difficult for me to ascertain whether the observer is a member of the SPA, so my apologies if your name isn’t on the list of contributors above (if so, please write and set me straight).

The image above, taken by Dave Finnigan on 5 March at 21:15 using an 8-inch SCT and DMK21AU04AS CCD camera, shows one of the Moon’s most peculiar features. Known as Mons Rümker, this bubbling, blistering plateau with a diameter of 70 km rises from the smooth plains of northern Oceanus Procellarum and is best seen just after the morning terminator has uncovered it or just before it disappears into the evening terminator. A number of domes, each around 10 km in diameter, emerge on top of it, the highest of which rise several hundred metres above the surrounding mare. Mons Rümker may appear large and impressive when illuminated by a low Sun, but its slopes rise a gentle 5° or so. It can be viewed on the evenings of 1 July, 30 July and 29 August (sunrise terminator, with a very foreshortening libration) and the mornings of 15 July and 14 August (sunset terminator, favourable libration).

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