A magazine of lunar topographic studies Vol. 17 No. 2 December 2008

Edited by Peter Grego, Topographical CoordinatorAll observations, correspondence and copy to:4A Halimote RoadSt DennisSt AustellCornwall PL26 8BHUnited KingdomEmail: Peter.Grego@BAALunarSection.org.ukVol. 17 No. 2 December 2008The NewMoonA magazine of lunar topographic studiesAlan Tough (Elgin, Scotland) captured thisbeautiful image of the young crescentMoon adorned with the glow of earthshineon the evening of 2008 March 09.

Bruce Kingsley’s image of the Altai Scarp, taken on 2008 November 17 using a 280 mm SCT and Skynyx 2-0 CCD.ContentsPapers3 The lesser-known nomenclature of the crater Gassendi Nigel Longshaw6 Beginning lunar imaging Maurice Collins821Geology of the Rimae HippalusFeatures of the young Moon’s terminatorPhil MorganPeter GregoObservations11 Agatharchides A region Phil Morgan12 Agatharchides A region Phil Morgan13 Agatharchides A region Phil Morgan14 Hippalus, Campanus and Rimae Hippalus Grahame Wheatley15 Hippalus / Poisson Peter Grego16 Messier and Messier A / Wrottesley Peter Grego17 Region west of Marius Colin Ebdon18 Darwin Colin Ebdon19 Darwin Peter Grego /Phil Morgan20 Grimaldi and the ‘Miyamori Valley’ Phil Morgan24 Bailly / waxing gibbous Moon Sally RussellImages12Young lunar crescent with earthshinePiccolomini and the Altai ScarpAlan ToughBruce Kingsley23 15 day Moon, supersaturated Maurice CollinsPage 2 The New Moon December 2008

The lesser-known nomenclature of thecrater GassendiNigel LongshawSELDOM does one comeacross a lunar featurewhich has received as muchattention as the great ruinedcrater Gassendi situated onthe northern shores of theMare Humorum. As T. G. E.Elger (1836-97) wrote underSelenographical notes inThe Observatory (1890),“Mainly owing, it may besurmised, to the exceptionallyinteresting variety ofdetail on its floor, Gassendimay, next to Plato, claim tobe more favoured in thisrespect than any other formation.During the last 40years many distinct representations,of a more or lessvaluable type, haveappeared in various forms,mostly executed with a viewto display the marvelloussystem of clefts which ramifyamid the ridges and hillsin the interior and to drawattention to the equallyremarkable character of theborder and its adjuncts.”Named by GiovanniBattista Riccioli (1598-1671) using the spellingGassendus in honour of the French theologianand astronomer (1592-1655) thecrater forms an integral part of anydescription of this area of the Moon andwas described at length by many of theearly selenographers. Debate has ragedfrom the interpretation of its interior featuresto the forces which have shaped itsmorphology, it has been the site of severalTLP reports, P. Moore records in his Guideto the Moon (1953) that H. P. Wilkins(1897-1960) recorded a possible meteoricimpact observation on 1951 May 17 whenhe saw a ‘bright’ speck inside Gassendiwhich lasted one second and left a glowfor perhaps two seconds more. One authoreven claimed Gassendi’s central mountainsrepresent a giant letter ‘E’ ‘as perfectas if drawn by an architect’ suggestive ofintelligent life resident on the lunar surface!On reading observational reports andpapers in relation to this formation oneThe New Moon December 2008A sunrise study of Gassendi by E.Stuyvaert made on 1879 November 24.From the Annals de l’Observatoire deBruxelles, Volume 4, 1883.Gassendi, in all its‘telescopic glory’ asdepicted by E. L. Trouveloton Plate 20 of the Annalsof the Harvard CollegeObservatory (1873).comes across nomenclaturewhich has been appended toGassendi and its surroundings,nomenclature whichhas never been officiallyadopted yet in itself is worthrepeating as it adds a littlemore interest to the timespent at the eyepiece andreminds us of those selenographersto which we owe agreat deal. It is also apparentthat the formation forms thesubject of many observationaldrawings which havebeen published in the pasthowever I thought it wouldalso be useful to reproducesome of the lesser-knownrenditions made by authorswhose work seldom finds itsway into the mainstream literatureor lies buried inpapers seldom referred to inthe present day.One of the earliest studiesof the feature was by John Philips (1800-74) and was published in Volume 158 ofthe Philosophical Transactions of theRoyal Society (1869) illustrating his paperNotices of some parts of the surface of theMoon. A geologist, Philips first observedthe Moon through the great Rosse reflector,an experience so profound that ‘thereafterastronomy largely engaged his attention’according to Sheehan and Dobbins inEpic Moon. Philips described the telescopicappearance of Gassendi in some detailusing terminology later elaborated on byE. Neison (1851-1938) in his 14 pagemonograph on Gassendi published in theAstronomical Register Volume 11 (1873).According to Philips the walls of Gassendiare ‘everywhere rugged and fissured’,with the highest point being ‘on the eastern[classical orientation] border (9000feet according to Madler) where a sort oflacuna [hollow], rather than a crater occursin the middle of the crest’. This becomesPage 3

Above: A rare high sun study of Gassendi by H. Tompkins whichappeared in the English Mechanic, number 2618, 1915 May 28.The curious appearance of the three bright circular featureswould be worth checking under similar lighting these mayrepresent the central peaks and the two craters on the floorindicated on Trouvelot’s drawing.‘The Lacuna’ in Neison’s later paper and isdescribed as being ‘some 8 miles inextreme length and 4 in breadth, is notdeep, but of very irregular shape; andbears the appearance of being a space onthe wall enclosed by two ridges, ratherthan anything else’. Philips also describesthe northern part of Gassendi as beingcomposed of a ‘confluence of small ridgesfrom the interior, directed towards thespoon-shaped crater, marked A onMadler’s map’. Taken up by Neison thisbecomes the ‘spoon’ crater beingdescribed as ‘thirteen miles long by tenbroad is very deep, having very steep interiorslopes nearly 4000 feet deep: and fromthe walls several spurs or plateau’s project’.T. W. Webb (1806-85) wrote in correspondencewith W. R. Birt (1804-81) in1871 that he ‘ascertained one curious feature,the whole wall once occupying, as wemay suppose, the breach betweenGassendi and the ‘spoon’, has rolled downinto the interior of Gassendi and extendsas an ill-defined mass, half way to the central[mountain] group’.Exterior to the westernwall there is amountain spur unofficiallyknown as the‘Percy Mountains’, aname proposed by W.R. Birt in his paperentitled On the extensionof lunar nomenclature,MNRAS volume24 p.19-20,November 1863.Described by Elger as‘the bright highlandsextending east ofGassendi towardsMersenius, formingthe north eastern borderof the MareHumorum. Theyabound in minutedetail — bright littlemountains and ridges— and include someclefts pertaining to theMersenius rill system;but their most noteworthy feature is thelong bright mountain arm, branching outfrom the eastern wall of Gassendi andextending for more than 50 miles towardsthe south east" (all directions in Elger’sreport are of course ‘classical’ orientation).This mountain spur is designated as suchby Hugh Percival (Percy in many of hispublished works) Wilkins on his MoonMaps published in 1960. Wilkins’ chartscontain many names which he attemptedto have ratified by the InternationalAstronomical Union and accepted as officialnomenclature, whilst the name ‘PercyMountains’ has never officially accepted,and was not of his own making, perhaps itsofficial recognition would be a fitting tributeto a much maligned selenographerwhose success in resurrecting the BAALunar Section following the Second WorldWar is all to often overlooked.Observing early sunrise on the PercyMountains with my Questar telescope on2008 June 14 I thought the general form ofthe mountain range gave the appearance ofa corkscrew in the small telescope at lowpowers, which perhaps sits rather well juxtaposedwith Philips’ ‘spoon’ further to thenorth! Under a low Sun using a smalltelescope there is a distinct triangularshaped shadow which is formed south ofBelow: Two vignettes of Gassendi made by the author on2008 June 14 using a Questar 90 mm MCT x80 and x160.Seeing conditions: AIII.The ‘spoon crater’(Gassendi A) on the sameevening at colongitude45.28°. The triangularshapedshadow to thesouth (IAU) of the cratercan also be seen, muchas it was described by thecorrespondent in theEnglish Mechanic.Sunrise on the ‘PercyMountains’ at colongitude45.03°. The ‘lacuna’ isalso visible on the westernwall, as described byPhilips and Neison.Page 4 The New Moon December 2008

Gassendi A, this shadow is veryprominent, and appears somewhatstrange in its orientation.The surface relief to the eastappears a little shallow and it isdifficult to reconcile how such aprominent shadow might beformed. In the EnglishMechanic for 1910 June 10 onecorrespondent using a smallaperture telescope raised thequery ‘is there a high ridge ofhills to the south of Gassendi Ato account for this long pointedshadow?’ The Times Atlas of theMoon indicates a ridge extendingto the south of Gassendi Acoupled with a rille or valley atits base; this ridge and lowerground to the west is probablyAbove: Drawing by George H. Leonard onp.153 of Someone Else is On Our Moon(1977), according to him ‘an outstandingexample of a perfect E on the floor ofGassendi’.Above: Typical of Prof. L. Weinek’sdelightful lunar vignettes, this exampleappears, along with others, in a littleknownbook The Amateur Astronomerby Gideon Riegler (1910) and recentlyrediscovered’ by Richard Baum.responsible for the lingering shadow spirein this region.With the level of attention this formationhas received in the past it would be feasibleto compile a detailed record of pastobservations, observations which resoundto the same controversies which plaguedformations such as Plato, Linné andEratosthenes. There is a level of truth inthe old selenographical saying ‘every manhis own Gassendi’, the ability to detect thefiner detail on the crater floor is dependentupon the instrument used, the illuminationat the time of the observation, seeing conditionsand of course the individualobserver, it is perhaps understandable whyso many differing interpretations anddrawings have be made, the result ofwhich all to often suggested evidence forchanges on the lunar surface to thosereceptive to such ideas.The purpose of the preceding brief outlineis simply to bring to light and compilea number of long lost references and hopefullyencourage time to be spent at the eyepiece,once stationed at the telescope perhapsthe observer will take pleasure insimply recording what they can see, nomatter how strange a feature might initiallyappear, there is a good chance someonehas recorded something similar in the past.Left: An impressive study of Gassendiby J. W. Durrad on 25 January 1877,featuring on p.287 of WalterGoodacre’s book The Moon (1931)The New Moon December 2008Page 5

Beginning lunar imagingMaurice CollinsIhave recently been contacted by someonewho is interested in getting intolunar imaging, so I have been thinkingabout how I started, and giving him sometips. I thought may be worth sharing witha wider audience also in case there is anyoneout there who may be under theimpression that it is something way toodifficult or expensive for them to do.Firstly, do you have any sort of still digitalcamera that you use for family photos,holidays etc? Even a mobile phone camerawill work. If you do have a digital cameraand a good eye relief eyepiece of fairlylong focal length, you are all set to make astart. To begin with, a 25 mm to 17 mmeyepiece works well, but you can use up tothe limit of your telescope as long as thecamera can see through it.To take images, simply point the camerathrough the eyepiece, holding it by hand.To find the Moon with the camera lens,which can be a bit tricky, back off a bituntil you see the bright spot of the Moon’simage on the cameras LCD screen, thenbring it down closer, but never actuallytouching the two lenses together (thoughno harm seems to be done if they dobriefly touch). Put one finger on the side ofthe eyepiece to steady the camera in place.It does not cause as much vibration as youwould expect and helps keep the Moon inthe field of view while taking the photo.Next, focus the telescope, as the focus ofyour eye at the eyepiece is different towhat the camera sees — for me it is a reasonablylarge change of telescope focus.Then use the camera’s zoom function(either digital or optical zoom is okay) toframe out the black eyepiece field stop thatvignettes the image so that you only seethe lunar surface on the LCD of the camera,or at least only the edges of the frameshowing black. Gently press the shutterwhile holding your breath so as not to giggleanything. Oh yes, and remember todisable the flash! And voila, you shouldget a very nice image of the whole disk orpart of the Moon. If it looks too bright andsaturated, or too dim and grainy, check theEV settings on the camera and go up ordown a couple of settings to see whatworks best for that phase of Moon.Take lots of shots. Some will be blurry,some will be sharp, and the more you havethe better you will get a good one out of it.You can then process the images on yourcomputer to reduce the size to sharpen itand run the other image processing functionsover it to get it looking good.Sometimes the images look better ingrayscale, sometimes the good ones looknice in color.The technique described above is theeasy way into lunar astrophotography. Ifyour camera has an AVI movie mode, youPage 6 The New Moon December 2008

Maurice Collins’ image of the morning terminator on 2008 July 10, using a Fuji A800 (8.3 megapixel digicam) and 200 mm SCT.are even one step up and can just record avideo sequence which you can then stackusing a program like Registax to get reallysharp images that you can mosaic togetherif you like. This works for planets too.This way, I recently obtained a really niceshot of the crescent Mercury showing itsphase. You can even use a video camera,and convert the camera files to AVI andthen do the stacking. I have only used thisfor a lunar eclipse and thin crescent Moonbut it works, though a bit more work isinvolved.The New Moon December 2008The next step up (and easier way) is withthe a modified webcam or astronomicalCCD camera such as the Meade LPI(Lunar and Planetary Imager). No eyepiecesare needed, just the camera at primefocus and you can add a Barlow lens if youwish to increase the image scale.Think simple, and it usually works. Alsoif someone says to you: “You can’t do itthat way!” ask “why not?” Break the rules(if there are any hard and fast ‘rules’) andexperiment to see if it works. You don’tyou need brackets and fancy CCD camerasto do lunar astrophotography. If you havethem, all the better, but if you don’t, lunarimaging is still something you can do.I now use the Meade LPI to do my lunarimaging, and much of it is done remotely,but it wasn’t too long ago that I was usingthe simplest methods outlined here to takepictures of the Moon, so before I forget mybeginnings I thought it worth sharing withothers. I hope this helps someone in gettingstarted who would otherwise not thinkof trying it, using gear they may alreadyhave around home.Page 7

Geology of the Rimae HippalusPhil MorganTHE Mare Humorum (Sea of Moisture)is a circular basin roughly 400 kilometresin diameter, dating to the Nectariangeological period of lunar history, and likethe other circular Maria is a site of a positivegravity anomaly. In the late Imbrianera its interior was flooded by mare lavaproducing fine arcuate wrinkle ridges, particularlyaround the eastern half of thebasin, probably as a result of compressivestress. This compression produced a correspondingzone of tension around theperiphery of the basin, the results of whichwe can see today as a series of (mostly)arcuate rille systems, namely the RimaeAgatharchides, Hippalus, Mersenius andDoppelmayer. This article deals with theRimae Hippalus, in particular the regionaround the small crater Agatharchides A.Formed by crustal dilation and tectonicmovement of crustal blocks, the RimaeHippalus are a roughly parallel series ofgraben-type rilles that mark the easternboundary of the basin spanning a distanceof some 250 kilometres. Best observed ataround colongitude 35° onwards at sunriseand about colongitude 200° onwards atsunset.Starting at the north at the old floodedcraters Agatharchides and Agatharchides Pas a trio of rilles, the Rimae Hippalus IIand III skirt around the crater of that name,whilst the Rima Hippalus I slices throughthe centre of it in a beautiful concentric arcas it heads towards the south. At this pointthey are joined by the shorter rille RimaHippalus V, and all peter out as they strikesouth towards the crater Vitello.Observationally, most of my studieshave been centered round the small, butinteresting (18 km) crater AgatharchidesA. This crater was named Moore byWilkins, and in 1949 Patrick Moore (nowSir Patrick of course) discovered twodusky bands running up the inner west(IAU) wall of the crater using a 6-inchrefractor. Since this crater sits directly ontop of the Rima Hippalus II and there is nosign of the rille cutting through either thecrater floor or its ramparts, we can assumethat the crater is the younger of the two(though it’s not always emphatically thecase that that one feature overlying anotheris always the younger!)To the west of Agatharchides A the RimaHippalus II shows a considerable displacement.This break is not visible under earlysunrise conditions as it is hidden by thelong shadows striking westwards fromAgatharchides A. Just south of this displacementthe rille forks into two and theeastern branch runs northwards into thesouthern outer rampart of A. In fact thisarea is the centre of a zone of fracturingthat is radial to Mare Humorum and iscomplimentary to the more obvious concentricarcuate Hippalus rille system.Another dislocation sits directly underAgatharchides A. As the Rimae HippalusIII heads south it meets the north outerrampart of Agatharchides A, passes underthe west (IAU) wall and emerges to thesouth, curving to the west just east of theRima Hippalus III dislocation mentionedabove. Lunar maps show the RimaHippalus III continuing on south ofAgatharchides A, but I believe this sectionof the rille was never connected directly tothe shorter north segment, although visuallyit does appear to do so to the Earthbased observer. Similar fractures can beseen along the Rima Hippalus I insideHippalus itself, and to the north. All aredextral (right handed) in their displace-The Hippalus area, mapped by Walter Goodacre in 1910 (left) and Percy Wilkins in 1946 (right). From the collection of Peter Grego.Page 8The New Moon December 2008

ment. Just east of Agatharchides A anothershallow rille runs south and is bisected bythe Rima Hippalus IV. This rille is alsofractured along its length, herringbonefashion (see Lunar Orbiter image IV-132at right).As the Rima Hippalus III strikes southwardsbeyond Agatharchides A, the rilleskirts a small hill, recorded sometimes ashaving a summit craterlet. Observationallyat least, the rille at this point has a pronouncedbend eastwards. It is interestingto note that this sharp ‘bendaround’ is notconfirmed by the overhead Lunar Orbiterimages, although many observers haverecorded it as such in the past. Rükl alsoshows no great curvature here, though forthe most part he based his charts on theLunar Orbiter photos. This apparent lunarillusion is shown well on my drawing of2004 March 1 (see p.12). Allowing for thisrille’s position on the lunar sphere, some30° west of the Moon’s central meridian,and the resultant distortion in its shape(curvature), we would expect the bend ofthe rille around the small hill to appear lessto the Earth bound observer, and not, as isapparently the case, much more. Furtherstudies by myself show that a section ofthe eastern half of the hill has fallen orslumped into the bottom of the rille.Whilst the extra shadow that this fallensection casts eastwards could explain anapparent increased curvature of the rille atAbove: Lunar Orbiter photo IV-132, at col. 48.66°. Credit: NASA.Below: Part of LAC 93 (featured on p.79-80 of The Times Atlas of the Moon) showingMare Humorum and Rimae Hippalus. North is at top. Credit: NASA.The New Moon December 2008Page 9

sunset, it couldn’t do so at sunrise. In factthe shadows falling eastwards from thehigher part of the hill at sunset largelyobscure any chance observing this illusion atlunar dusk.Other features of interest in this regioninclude the narrower Rima Hippalus IV. Thismuch more difficult to observe rille runsnorth eastwards diagonally from the aforementionedsmall hill for some distance, andis a line of demarcation between two areasof differing tone. To the south of this, andalmost parallel to it, is another even finer,and unnamed difficult to observe rille. Asthe Rima Hippalus II and III run north fromAgatharchides A, there is a fairly broad butshallow rille connecting the two diagonallyat roughly the same angle as the RimaHippalus IV further south. This is shownfaintly on p.80 of The Times Atlas of theMoon (LAC 94).To sum up, this is a particularly interestingregion of the Moon to study, and one doesn’tneed a particularly large telescope toobserve most of the finer features mentionedabove. Perhaps those observers that likeCCD imaging as well as a bit of a challenge,could attempt to unravel and explain themystery of the ‘bendaround’ rille?Right: Part of LAC 94 (featured on p.79-80of The Times Atlas of the Moon) showingthe area to the east of Hippalus and most ofthe features mentioned in the article. Northis at top. Credit: NASA.Below: Detail from a map of the Hippalusarea by the great observer P. B.Molesworth (1867-1906), presented withnorth at the top for easier comparison withthe LAC map.Page 10 The New Moon December 2008

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Hippalus, Campanusand Rimae HippalusHippalus, Campanus and Rimae Hippalus2000 January 1620:05 to 21:15 UTCol. 34.6° to 35.2°Moon’s age 10.1 dLunation 953Seeing: AII, AI at timesTransp: Generally good, clear and cold240 mm f/9.8 Newtonian x235Grahame WheatleyLocation: Long Eaton, Nottingham, UKPage 14 The New Moon December 2008

Hippalus2008 December 720:10 to 20:45 UTCol. 31.6° to 31.9°Moon’s age: 10.1 dLunation 1063Seeing: AII-III, some mist200 mm SCT x200, binoview, integrated lightPDA sketch (north at top), enhanced inPhotoPaint immediately indoorsPeter GregoLocation: St Dennis, Cornwall, UKNotes: Hippalus had just begun to emerge fromthe morning terminator. I was intrigued by thenetwork of faintly illuminated patches on thefloor, which was mainly in shadow. None of theRimae Hippalus were immediately obviousowing to the shallow illumination and abundanceof shadow. A broad dark band of shadowran from north to south across Hippalus andextended further south, blending into the terminator.Hippalus’ northwestern rim appeared asa bright line. To the southwest, the peaks of Promontorium Kelvin jutted out of the shadow, alongwith several peaks south of Hippalus. Another set of illuminated peaks could be seen north ofHippalus. A dusky tract where Rima Hippalus II lies was visible to the northeast betweenHippalus’ northeast wall and Agatharchides A, and only part of the Rima Hippalus III was visible.Poisson2008 November 1901:40 to 02:15 UTCol. 162.7° to 163.0°Moon’s age 21.1 dLunation 1062Seeing: AII, clear skies300 mm Newtonian, x100 x200PDA sketch (north at top)enhanced in PhotoPaintimmediately indoorsPeter GregoLocation: St Dennis, CornwallNotes: The unusual kidneybeanshape of Poisson is evidentlyvery ancient and overlainby several smaller craters,namely Poisson A and T in thenorth and west and Poisson U and V in the south. Poisson’s floor, most of which was illuminatedby the late afternoon sunshine, appeared somewhat hilly. A sizeable unnamed crater about 50 kmin diameter appeared to lie to the southeast of Poisson. Apianus lies just north of the area drawn,its southern edge depicted. To the far west is the eastern rim of Aliacensis.The New Moon December 2008Page 15

Messier and Messier A2008 December 15-16 / 23:50 to 00:15 UTCol. 130.1° to 130.3° / Moon’s age 18.3 d /Lunation 1063 / Seeing: AII, some mist200 mm SCT x200, binoview, integrated lightPDA sketch, enhanced in PhotoPaint indoorsPeter Grego / St Dennis, Cornwall, UKNotes: Both craters were largely filled withshadow cast by their western rims. Messiercast a long twin-pointed shadow eastwardacross the mare for around 15 km. The internaleastern wall was not particularly brilliant.Messier A’s inner eastern wall was the brightestpart of the area depicted, a crescent withno discernable terracing or structure. It casttwin lobes of shadow around Messier’s northwesternand southwestern ramparts. The rayextending westward from Messier A was notprominent and its dual nature was not particularlyevident near to the crater. Subtle shadingwas observed elsewhere in the country aroundthe crater pair, with delicate fans of light anddusky albedo radiating out from both.Wrottesley2008 December 15 / 00:20 to 00:55 UTCol. 118.1° to 118.4° / Moon’s age 17.3 d/Lunation 1063 / Seeing: AII, clear and cold200 mm SCT x200, binoview, integrated lightPDA sketch, enhanced in PhotoPaint indoorsPeter Grego / St Dennis, Cornwall, UKNotes: Wrottesley was half filled with eveningshadow, its central peak showing as a singlebright dot. Some structure was discerned on itsinner eastern wall, in part radial shading linkedto deformities in the outline of the eastern rim.The northeastern part of the inner wall wasbright. East of Wrottesley was Petavius’ rim,inside the shadow of which was seen intricateslivers of illumination corresponding to highpoints in Petavius' inner wall terracing. A curvinglow ridge extended north of Wrottesley andconnected with an elongated crater shown nearthe top edge of the sketch. The area toWrottesley’s southwest was complicated, andwhat’s shown is only a general impression. Itappeared to consist of low ridges correspondingto an ancient and degraded crater over whichWrottesley is overlain. The plateau northwest of Wrottesley cast a dark curving shadow. Its heightswere complex and the main feature seemed to be a large depression like an old crater.Page 16 The New Moon December 2008

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DarwinDarwin2008 October 12 / 20:20 to 21:10 UTCol. 69.3° to 69.8° / Moon’s age 13.5 d /Lunation 1059 / Seeing: AII-III, slight mist200 mm SCT x200, binoview used,integrated lightPDA sketch, enhanced in PhotoPaint indoorsPeter Grego / St Dennis, Cornwall, UKNotes: A good libration for a general study ofDarwin, a vast and ancient crater near thewestern limb. The crater was emerging intothe morning light during the session. Some ofits northern floor was visible, in the form ofwhat appeared to be a large area of raisedground, subtly shaded on its eastern face.Darwin's southern floor was completely coveredwith shadow, the southwestern rim beingvisible as a narrow, complex line of illumination.The dark-floored crater Crüger was visibleto Darwin's northeast. A narrow linearshadowed scarp ran from Darwin's northeasternrim, extending south and east of Crüger.Parts of the southern extension of RimaSirsalis was visible running from the southeasternrim of Darwin, north to de Vico A, withhints of it further north to Crüger A, but indistinctlyseen here.The New Moon December 2008Darwin2008 October 12 / 21:30 to 22:15 UTCol. 70.2° to 70.5° / Moon’s age 13.5 d /Lunation 1059305 mm Newtonian, x400Phil Morgan / Tenbury Wells, Worcestershire,UKIt’s not often that three people, observing independentlyof each other, make visual studiesof the same feature on the same evening atabout the same time. This is what happenedon the evening of 2008 October 12, whenColin Ebdon (p18), Peter Grego (above, left)and Phil Morgan (above) depicted the largecrater Darwin as it emerged from the morningterminator. Libration was excellent on thisoccasion, with libration in latitude at around-03° 10’ and libration in longitude -05° 50’.Page 19

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Features of the young Moon’sterminatorPeter GregoMareHumboldtianumGaussPlutarchCannonNeperSchubertKastnerAnsgariusHecataeusThe New Moon December 2008HumboldtLeft: TheMoon’s easternlibration zonecentred on90°E. FromNASA chartLPC-1.AMONG the thousands of lunar observationaldrawings to be found in the current archivesof both the SPA Lunar Section and the BAA LunarSection’s Topographical Sub-section, it may surprisethe reader to learn that there are no detailedvisual depictions of features on the very young(sub-36 hour) lunar terminator. As far as imagery isconcerned, photographs of the young lunar crescentare usually rather indistinct and blurred.The narrow sliver of a sub-36 hour lunar crescentis not easy to spot. The observer’s location andlocal horizon, weather and atmospheric conditions,the season, timing of new Moon and the Moon’sangular diameter all have to combine favourably tomake the attempt worth trying. UK-basedobservers are most favourably placed to make thesearch for young lunar crescents during the spring,when the ecliptic makes its steepest angle to thewestern horizon. Since the Moon always lies closeto the ecliptic it will be at its highest above thehorizon after sunset, while the Sun drops quicklybelow the horizon and skies darken rapidly. Thehigher the Moon at sunset, the less atmosphericmurk its light has to compete with, and the observer’schances of discerning it are improved. Thecontrast between the dim crescent and the duskskies is not great, even under the clearest conditions;the presence of atmospheric haze will causeextinction near the horizon, reducing the chancesof seeing this elusive phenomenon. It also helps toPage 21

have a Moon near perigee, since theorbital motion of the Moon is at its fastestand it will have moved further from theSun following new Moon in a given periodof hours.The sub-36 hour Moon presents a dim,thin partial crescent shimmering with turbulence.Because the Moon is not a perfectsphere, the very young crescent neverextends to a full semicircular arc aroundthe limb — the shaded areas of high reliefon the Moon’s terminator are facing theobserver and block out some of the sunlitportions behind them, and this effect ismore pronounced towards the horns of thecrescent where the Moon is narrower.Andre Danjon (1890-1967) calculated valuesfor the ‘deficiency arc’ — the extent towhich the crescent varies from a semicircledepending on its elongation from theSun. A 180° crescent can only be seen atelongations exceeding 40°. Actually, atlarger elongations in which the Moonpresents a wider crescent, the deficiency isof a negative value, which produces an arcslightly longer than 180°, the ends of thecrescent extending to produce the phenomenonof ‘Saber’s Beads’ (see above).At elongations of less than 40°, the lunarcrescent gradually gets smaller until, at anelongation of 7° the deficiency arc is also7°, and the illuminated portion of theMoon cannot be seen at all.When the Moon is under a day old, justbeing able to see the Moon is a feat initself, and it isn’t really possible to identifyany of the Moon’s features with certainty;observers might want to estimate thesize of the crescent and make a sketch ofany peculiarities in its outline. Imagersmay record the phenomenon using digitalcameras, and perhaps they will even showthe earthshine on the Moon’s unilluminatedface. Half a day later, when the Moon isaround 36 hours old, it has become possibleto readily identify lunar features telescopicallyor by comparing an image to asuitable map.On 2008 September 1, at 06:55 UT,Maurice Collins (Palmerston North, NewZealand) managed to capture the 1.45 dayold crescent Moon as it came out of theclouds just 5° above the horizon (springtimein the antipodes). Using a 200 mmSCT (C8) and LPI CCD camera, Mauricecaptured a number of images and performeda manual mosaic in Photoshop.The result is an excellent image of the veryyoung crescent Moon in terms of theamount of clearly discernable topographicdetail. The image is all the more valuablebecause libration for the eastern limb wasvery favourable at the time. A number offeatures have been identified on the image(see p.21).I would be interested in seeing moreobservational drawings and images of featureson the very young crescent Moon, so‘Saber’s Beads’. At the beginning ofLunation 1040 Nigel Longshaw(Chadderton, Oldham, UK) made thisobservation of the Moon’s southern cuspshowing a number of detached illuminatedpoints beyond the main crescent. Thesepoints of light, reminiscent of the solareclipse phenomenon of Baily’s beads,have been referred to as ‘Saber’s Beads’,after Stephen Saber, an American amateurastronomer who has drawn attention tothem. The phenomenon is easily visible afew days after new, but it is reportedlyvisible when the Moon is just a day old.Date: 2007 January 22Time: 18:35-45 UT Seeing: AIIIInstrument: 66 mm APO (WilliamOptics ZS 66 mm SD) x97Notes: The Moon’s southern cusp isoften a beautiful sight during the first fewdays at the start of a lunation; however Icannot recall seeing so many ‘detached’illuminations in the past. The little refractordealt amiably with this difficult observation,and contrast remained excellent,despite poor seeing. Earthshine took on a‘smoky'’grey/green hue particularly to thesouthern pole and western limb.if you have made them in the past, pleasedo send them in. Such observations andimages, made at (or beyond) the limits ofwhat might be considered acceptableobserving conditions, may bring to lightpreviously visually unreported topographicalfeatures. A Wratten #21 orange or#23A light red filter will help increase thecontrast between the twilight sky and thefaint lunar crescent (this applies to visualobservation as well as imaging).Features to attempt to look out for duringfavourable librations include the westernedge of the major crater Schrödinger andthe Vallis Schrödinger (neither of which Ihave read about actually being discernedvisually) extensions of the cusp in thesouth polar region beyond Amundsen, andshadows cast by the eastern borders ofMare Smythii, Mare Marginis, MareHumboldtianum and Belkovich and theshadows of the asemblage of infilledcrater-plains which makes up MareAustrale.Of course, the same elusivity applies tothe Moon’s western limb very late on inthe lunation, but under opposite circumstances.On the whole, however, sectionrecords for late lunation observations fromthe UK are much poorer in terms of quantity,but in terms of quality they tend to bebetter, since more dedicated and skilledobservers will tend to make the effort toobserve late on in the lunation.Page 22 The New Moon December 2008

Maurice Collins writes: Blue areas are high Titanium, reds are very-low Ti rocks. Mare Frigoris and the region in Imbrium aroundthe Apennine bench formation seem to be quite red and perhaps rich in these rocks. The reddish creamy rocks of the highlands eastof Tycho underlying the younger rays and other ejecta there is quite interesting. The rays from Langrenus are quite startling.An invitation to joinThe BAA Lunar Section Topographical Subsection Yahoo GroupThe free and timely distribution of observations is important, and there’s only so much that canactually be published in the Lunar Section Circulars and The New Moon.A new Yahoo group has been set up for the BAA Lunar Section’s Topographical Subsection — aplace where members can post their observational drawings, share files and discuss mattersrelated to visual lunar observing. All visual lunar observers are invited to join us at:http://uk.groups.yahoo.com/group/baalunarsection-topography/At the time of writing the group has 16 members and more than 150 lunar observations havebeen posted there — thanks to all those who have joined!Peter GregoThe New Moon December 2008Page 23

Bailly2008 October 1221:00 to 22:00 UTCol. 69.7° to 70.2°Moon’s age 13.5 dLunation 1059105 mm OG, x240Sally Russell / UKBaillyWaxinggibbous Moon2008 October 1121:20 to 22:30 UTCol. 57.7° to 58.3°Moon’s age 12.5 dLunation 105970 mm OG, x30Sally Russell / UKPage 24 The New Moon December 2008