Vol 49, No 4, April 2012 - BAA Lunar Section

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It was a pleasure to see a contribution from Barry Fitz-Gerald, who was an active member of the Lunar Section some time ago and who has now returned to the fold. Barry’s piece on Catena Krafft shows the value of careful analysis of the vast repository of spacecraft imagery now available online. His view that Catena Krafft cannot be a secondary crater-chain originating from Krafft is undoubtedly correct, since it clearly impinges upon the floor and walls of that crater. The problem traditionally associated with regarding it as a secondary feature from Cardanus has been the fact that it is clearly not radial to Cardanus. I did wonder briefly whether it might be a secondary feature from Orientale, but the alignments don’t work out. Barry’s view that, along with the craterchain to the west with which it forms a triangle based on the N rim of Cardanus, this might be evidence of an oblique impact is certainly worth considering and I can think of no alternative account that fits the observational evidence. I am less persuaded by the suggestion that the central ridge crossing the floor of Alphonsus might be the result of an oblique impact that produced neighbouring Arzachel. The alignment of the ridge with other impact scars in the area suggests that, even if it is a deposit feature, it is more likely to have come from the impact that produced Imbrium. The evidence for oblique impacts on the Moon is growing daily (hardly surprisingly, since such impacts must have been plentiful), and there is much more evidence to be found both at the eyepiece and on images. On the question of impact ejecta, I attach an image of the crater J. Herschel, taken on 2012 February 3 (shown on the front page). Despite the poorish seeing, what immediately struck me was the unusual nature of the rubbly infill that litters the crater’s interior (also shown in the LRO image below). This is presumably ejecta from Imbrium, and it is clear that J. Herschel took a real battering. However, although the SE half of the interior looks more or less as you might expect under such circumstances (apparently randomly distributed mounds and secondary impacts, including chains pointing back towards Imbrium), the NW half shows strange patterns in the distribution of ejecta material. It almost looks like martian dunes arranged in curved, arcing formation—and it does not appear to point a finger back at Imbrium. Moreover, there appear to be fewer secondary impact craters in this half. Chuck Wood has suggested that this effect is caused by the tendency of impact ejecta to ‘swirl’. Further analysis of existing imagery, both Earth-based and spacecraft, might help shed further light on this. So, plenty of things to think about and to direct our observations! Bill Leatherbarrow J. Herschel, imaged by LRO. Image: NASA / LRO LROC team. Director, BAA Lunar Section 2 BAA Lunar Section Circular Vol. 49 No. 4 April 2012
Topographical notes compiled by Peter Grego Visual studies and observations Since March’s LSC, visual topographic lunar observations have been received from Peter Grego (St Dennis, UK), Chuck Hastorf (Arizona, USA), Philip Jennings (York, UK) and Phil Morgan (Tenbury Wells, UK). Some of these observations and accompanying notes are reproduced below. A note on submitting visual observations All visual observations should, in the first instance, be sent to the Director, Bill Leatherbarrow, by regular mail or, as is far more frequently the case these days, as email image attachments (Bill’s address is on the last page). If possible, please copy me in on the email with the attachments at editor@baalunarsection.org.uk, as it saves Bill the need to send them on to me for consideration for inclusion in the LSC. Please note that while observations are encouraged to be posted to the Lunar Section Visual Studies Yahoo! Groups website http://uk.groups.yahoo.com/group/baalunarsection-topography/ it’s important not to regard this as the official Lunar Section archive or the primary repository for observations. The site is meant to be an adjunct to the main work of the Lunar Section, and serves as a forum, so please ensure that if you do post observations there, also to send them to the Director (and me if possible). That way, nobody’s work will be missed and it will be officially archived, available for comment and analysis. Clarity in labelling image and observation files is important, both to avoid ambiguity and confusion and to make filing, archiving and accessing material easier and more efficient. Ideally, all image files should contain unambiguous date and time data, feature observed, instrument used and observer name. Other information pertaining to the observation, such as colongitude and libration, should be included in the covering notes, along with a written description (if any) of the observation. Vallis Alpes and possible dome in Montes Alpes, 2012 March 29 Philip Jennings The last time I sketched this region I lingered on the area for too long, resulting in inaccuracies caused by previously invisible features popping up half-way through the session. To avoid making the same mistake this time round, I drew very quickly. Even so, it took me 75 minutes to complete my drawing. Under such a low illumination, I couldn’t find an accurate template to help me position features accurately, so I hope it looks about right. The valley was looking spectacular, but one feature that caught my attention that evening was a small, circular ‘bump’ amongst the mountains (arrowed), apparently very low. I doubt it would be very evident at all if the angle of illumination was much higher. Could this be a rare example of a highland dome Full Moon at perigee BAA Lunar Section Circular Vol. 49 No. 4 April 2012 3
Page 1: Director: Bill Leatherbarrow The Br
Page 5 and 6: Sunrise on Plato Nigel Longshaw In
Page 7 and 8: Encke, 2012 March 03 Peter Grego No
Page 9 and 10: Join us at our Yahoo! Group: Lunar
Page 11 and 12: Images Since March’s LSC, lunar i
Page 13 and 14: (detail below) BAA Lunar Section Ci
Page 15 and 16: Peter Oden took this detailed image
Page 17 and 18: BAA Lunar Section Circular Vol. 49
Page 19 and 20: Figure 1. A modified sketch of Aris
Page 21 and 22: 2012-Apr-06 UT 00:21-04:04 Ill=99%
Page 23 and 24: Graze occultations ZC 1198 on 2012
Page 25: Lunar data for April 2012, lunation

Vol 49, No 4, April 2012 - BAA Lunar Section

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