MOON­WATCH

Sky at Night Magazine - - THE SKY GUIDE -

Ed­ding­ton is a large fea­ture which ap­pears very close to the Moon’s west­ern limb as seen from Earth. This means it’s af­fected by the Moon’s li­bra­tion state, the ap­par­ent rock-and-roll mo­tion which al­lows us to ac­tu­ally see 59% of the Moon’s sur­face over time.

It’s a crater that has been flooded by lava, re­sult­ing in a lu­nar fea­ture known as a walled plain. Its vast 134km di­am­e­ter is ringed by high­land ma­te­rial, most ob­vi­ous to the north and west. The eastern rim be­comes quite thin, mak­ing it tricky to see vis­ually. To­wards the south­east, the rim all but dis­ap­pears into the lava of the Oceanus Pro­cel­larum.

As you view Ed­ding­ton, marvel at the fact that it has a di­am­e­ter equal to the dis­tance from Birm­ing­ham to Cardiff. Un­der the cor­rect light­ing conditions, when you move your gaze closer to the limb it be­comes ev­i­dent that al­though large, Ed­ding­ton is dwarfed by the less dis­tinct form of 171km

Struve to its im­me­di­ate west. Struve is so mas­sive that the for­mer des­ig­na­tion of Ed­ding­ton was Struve A.

Un­like Ed­ding­ton’s dark and fairly dis­tinc­tive floor, Struve is harder to dis­cern be­cause it’s cov­ered in lighter ma­te­rial dis­guis­ing its ap­pear­ance. There are sev­eral small but dis­tinc­tive craters within Struve that stand out. These in­clude Struve C (11km),

Struve G (14km), Struve L (15km) and Struve M (15km).

Struve F (9km) and Struve K (6km) sit on the rim wall which di­vides Struve from Ed­ding­ton. There­after, pass­ing into the area bounded by Ed­ding­ton’s rim, there’s a dis­tinct lack of fea­tures. A num­ber of re­ally small crater­lets pock­mark Ed­ding­ton’s floor but these are dif­fi­cult to see with smaller in­stru­ments. The largest and most iden­ti­fi­able crater within Ed­ding­ton’s rim is 12km

Ed­ding­ton P but it is dark, like its pri­mary, and eas­ily over­looked. All that re­mains of Ed­ding­ton P are two sec­tions of rim, one to the east and one to the west. If we could view the crater from above, it would ap­pear like a pair of brack­ets.

Im­me­di­ately to the east of Ed­ding­ton lies the dis­tinc­tive 43km Seleu­cus. This is a lovely cir­cu­lar crater with a wide, ter­raced rim, a flat floor and a cen­tral moun­tain com­plex. A nar­row out­line of ejecta frames the crater, which sug­gests that Seleu­cus ex­isted be­fore its sur­round­ings were flooded with lava. The So­viet craft Luna 13 touched down on the Moon on Christ­mas Eve 1966 and its land­ing site is lo­cated ap­prox­i­mately 50km to the south­east of Seleu­cus.

The best view of Ed­ding­ton oc­curs – as is the case with many lu­nar fea­tures – when the Sun is low in its sky. This is typ­i­cally when the phase is ap­proach­ing full Moon or new Moon. At this time of year, early ris­ers are re­warded with a de­cent view of the wan­ing cres­cent, which re­sults in a lovely pre-new Moon view. This co­in­cides with the north­ern hemi­sphere’s au­tumn plac­ing the early morn­ing, wan­ing cres­cent Moon higher in the sky than at any other time of the year.

“A crater with a di­am­e­ter the dis­tance of Cardiff to Birm­ing­ham”

Ed­ding­ton pic­tured with its neigh­bours, Seleu­cus and Struve

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