June 6, 2020

AstroEvent: Exploring the Lunar Apennines & Ina Caldera.

Ina Caldera as seen from LRO. (Credit: NASA).

Whew! With yet another “Super-Moon” weekend has come and gone, and lunar exploration can now be safely left up to those who know and love the Moon. This week, as said Full Moon gives way to waning gibbous, I’d like to draw your attention to a famous mountain range on the edge of the Mare of Imbrium. The Lunar Apennines or Montes Appenninus lie at the edge of a volcanic scarp and feature some of the largest peaks on the Moon rising as high a 5 kilometers above the surrounding terrain (there’s no sea-level on the Moon). [Read more...]

Astro-Challenge: Hunting the Curtiss Cross.

Curtiss Cross finder chart (Photos by Author).

(Note: the images included are an obverse view as seen through our Schmidt-Cassegrain Telescope!)

Ahoy, mateys… just in time for September 19th and Talk Like a Pirate Day, we set our scurvy-clouded sights on a Lunar Cross worthy of emblazoning any skull-capped flag…

Up for a lunar challenge? This week, we look at a bashful feature that few have seen, and fewer still have reliably photographed; The Curtis Cross. This illusive feature lies just north of Fra Mauro and Parry (With an “A”) crater on the edge of the Mare Cognitum region. If the Fra Mauro region sounds familiar, that’s because it was the site slated for the aborted Apollo 13 landing, which was eventually performed on Apollo 14. In fact, the Curtis Cross formation sits within 100 km of the Apollo 14 landing site. The first informal reference to this particular formation, also sometimes referred to as Fra Mauro Zeta, seems to date from a mention in the June 1958 Sky & Telescope by Robert Curtiss. Unlike other “Cross” formations, the Curtiss Cross does not appear at the confluence of multiple crater rims; the Curtiss Cross instead appears to be a combination of broken mountain ridges and a string of crater chains. A “double dot” pair of the overlapping craters named Fra Mauro H & HA make a good visual cue, as these form one vertex of the “X”. Favorable illumination of the Curtiss Cross seems to occur around 14 hours after last quarter phase, which this month coincides with 3:49AM UTC on September 21th and thus will favor early AM viewers at European longitudes. (For an exhaustive list of predicted illumination dates, click here) OK, we’ve never seen this elusive feature either… be sure to send us pics, anecdotes, and general “tales of ‘yer hunt for this lunar whale of a sight!” (Yargh…)

…and don’t forget, ye landlubbers, that ye’ ole Autumnal Equinox occurs the Friday at 23 Sept 9:05AM EDT.

Lunar Orbiter view of the Curtiss Cross Region (Credit: NASA/LTVT).

The Astronomy Term for the Week is Chiaroscuro. No, this isn’t a Latina guitarist… time for a journey back to art class. Sometimes referred to as Clair-obscur by the French, the Italian derived term Chiaroscuro refers to the heavy use of bright and dark contrast to enunciate form, such as is often seen in the stark, even gloomy paintings of the Renaissance. The Moon, being a very black and white place, is rife for several brain illusions due to Chiaroscuro, and any student of lunar observations will “tell ye’ lassie that the moonscape ‘er appear the same twice…” (last of the pirate puns!)

Of course, optical illusions such as the Curtis Cross have drawn a fair share of UFO conspiracy theorists of the garden variety who think alien artifacts litter the Moon. (In contrast to the cranks who think we’ve never went?) Pareidolia aside, many of these illusions such as the Curtiss Cross can be attributed to the eye favoring stark, white features such as ridges, crater chains and scarps. A better discussion might be why we seem to favor “X” patterns in the jumbled landscape. Indeed, looking at a NASA close up of the region (See above-left) you can only see a passing resemblance to an “X” at full illumination; chiaroscuro at its best!