Skirting the western shore of the Mare Nectaris you will find three fascinating craters: Theophilus, Cyrillus and Catharina — all of which beautifully illustrate the evolution of lunar geomorphology caused by impact erosion. Turning the Celestron Omni 120 here last week (30.04.09) really was a treat and left me in no doubt about what I’ve been missing out on since I returned to amateur astronomy. The view just blew me away and I spent the next hour picking my way across the wreckage of this ancient landscape. See here for details: www.lpod.org
Theophilus was the first of my targets and the youngest of the crater trio which formed some time around the Eratostherian period. While the four jagged peaks of the impressive central mountain were clearly defined it was the intricate detail in and around the robust terraced walls that caught my eye. The contorted ridges that I could see radiated away from the smooth crater floor like ripples in a pool of water and made for an exceptional observation.
Lying to the south west, and slightly overlapped by Theophilus in the north east, the soft but tortured outline of Cyrillus marked itself out against the surface. This lunar relic dates from the earlier Nectarian period when the Moon was battered by massive impacts that created the major lunar basins. Looking within Cyrillus itself the three imposing mountains that rise around one kilometer from the floor of the crater stood out prominently, while the shadow filled Cyrillus A clung to the deteriorating south west verge. At this point I took a moment to examine Cyrillus’ wall’s and noted the state of deterioration, but it was nothing compared to Catharina’s decimated appearance.
An irregular and ruinous formation; Catharina presented itself in all it’s ramshackle glory not far from Cyrillus. This crater was also formed around the Nectarian period, but it was clear to see that it had suffered extensive damage from further impacts. The shadowy veil of Catharina P made a bold impression where it had obliterated the northern wall, while little remained of the crater embankment to the north east where Catharina B, and G had impacted. Casting my gaze towards the southern interior I easily spotted the dark silhouette of Catharina S watching over the remains of the crumbling rampart, while the shadowy outline of Catharina C embedded itself into the outer exterior of the crater.
There is so much detail to be had from this region of the Moon that it will keep you coming back again and again. If you want to study a good example of crater degradation then this trio will not disappoint. All are visible with 10×50 binoculars and personally speaking I have had some pretty good views through my 25×100 binoculars. However for seriously good observations a telescope in the region of 90mm and above will be needed.
To see Theophilus, Cyrillus and Catharina at their best I would recommend observing them when the Moon is either four to six days old, or when it is nineteen to twenty days old. So make sure you mark those times in your diary, and be sure to get out and take a good look at this display of “beautiful devastation”.
Tags: Catharina, Catharina B, Catharina C, Catharina G, Catharina P, Catharina S, Celestron Omni XLT 120, Cyrillus, Cyrillus A, Eratostherian, Mare Nectaris, Moon, Nectarian, Theophilus
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Up till now the weather conditions over Central Scotland during MoonWatch week have been reasonably decent. Sunday and Monday night were lost to partial cloud cover while I reluctantly let Tuesday night slip by so I could fulfill a minor, but pressing task. However, all was not lost as Wednesday served up another slice of sunshine and clear skies that brought the stars out to play later that evening.
With the Moon almost at it’s quarter phase, the view in and around the terminator was wonderful. There was also still a hint of some Earthshine, but it was less obvious than my last observation. Looking northwards the high crater walls of Eudoxus and Aristoteles looked imposing against the bright lunar surface while the rugged edges of the Mare Serenitatis and the diffuse Bessel ray just to the south were outstanding. Looking north east from here I could also easily pick out the prominent, almost circular outlines of Hercules and Atlas as they sat beyond the northern shore of the Mare.
Allowing my gaze to fall southwards I could just discern the Promontorium Agarum (a high mountainous cape) as it nestled against the east coast of the Mare Crisium whilst the Palus Somni (a large area of level, uneven terrain) could also be seen standing out against the dark grey basalt of the eastern Mare Tranquillitatis. As my eye’s wandered westwards I also observed the dark silhouettes of Plinius, Ross and Arago — a string of three isolated, minor craters — before I landed on the south west fringes of the Mare and the impact crater Delambre.
As I continued my descent ever southwards, the outline of the crater trio Theophilus, Cyrillus and Catharina was fairly obvious as they huddled together along the edge of the Mare Nectaris. Just west from Cyrillus I could see the smaller crater Abulfeda skirting quite close to the shadowy terminator.
Drifting across the hodgepodge craters of the southern highlands I could clearly see the impressive Maurolycus and the smaller Gemma Frisius just to the north, etched into the lunar surface like black jet. Barocius and Clairaut were visible just below as were the smaller craters: Breislak, Baco B and the slightly more prominent Baco. South east from here I could also see the contours of Pitiscus, Hommel, Vlacq and the smaller Rosenberger C as they clung to the lunar limb.
Besides observing the more evident lunar features, I also spent the time producing another rough drawing that I could use to help create a digital sketch of this marvelous scene. Here’s hoping the weather holds out so I can produce a few more.
Tags: Abulfeda, Arago, Aristoteles, Atlas, Baco, Baco B, Barocius, Bessel Ray, Breislak, Catharina, Clairaut, Cyrillus, Delambre, Earthshine, Eudoxus, Gemma Frisius, Hercules, Hommel, Mare Crisium, Mare Nectaris, Mare Serenitatis, Mare Tranquilliatis, Maurolycus, Moon, MoonWatch, Palus Somni, Pitiscus, Plinius, Promontorium Agarum, Rosenberger C, Ross, Strathspey 25x100, Theophilus, Vlacq
Posted in Astro Art, Observing | 2 Comments »