{"id":32817,"date":"2022-06-16T00:00:00","date_gmt":"2022-06-16T00:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/?post_type=purple_issue&p=32817"},"modified":"2022-07-12T14:58:47","modified_gmt":"2022-07-12T14:58:47","slug":"moonwatch-10","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/2022\/06\/16\/moonwatch-10\/","title":{"rendered":"Moonwatch"},"content":{"rendered":"\n

July\u2019s top lunar feature to observe <\/p>\n\n

<\/div>
\n

Kepler <\/strong><\/h4>\n\n\n\n

Type: <\/strong>Crater <\/p>\n\n\n\n

S<\/strong>ize: <\/strong>31km <\/p>\n\n\n\n

Longitude\/Latitude: <\/strong>38\u02da W, 8.1\u02da N <\/p>\n\n\n\n

Age: <\/strong>Less than 1.1 billion years <\/p>\n\n\n\n

Best <\/strong>time <\/strong>to <\/strong>see: <\/strong>Three days after first quarter (9\u201310 July) or two days after last quarter (23\u201324 July)<\/p>\n\n\n\n

Minimum equipment: <\/strong>50mm refractor <\/p>\n<\/div><\/section>\n\n

\"\"<\/figure><\/div>\n\n

Kepler <\/strong>is one of the great ray craters visible on the Earth-facing side of the Moon. Although it\u2019s smaller than those other superb examples, 93km Copernicus and 86km Tycho, Kepler gets a visual boost due to its location within the dark lava of Oceanus Procellarum, a 700km x 500km basin occupying a good portion of the western half of the Moon\u2019s face we see from Earth. <\/p>\n\n

Surrounded as it is by dark lava, the bright ejecta from Kepler stands out extremely well, radiating from the crater\u2019s sharply defined rim. Kepler\u2019s rim is impressive and rises to a peak height of 3,050m on the western side, the average crater depth being around 2,700m. Its sides appear to slope sharply down to a series of impressive, wide terraces. The overall appearance is not dissimilar to how an opencast mine would look from above on the surface of Earth. The western rim slope has been measured to have an incline of 42\u02da.<\/span><\/p>\n\n

\"\"
A careful look at Kepler\u2019s central region reveals what are probably best described as hills or mounds <\/figcaption><\/figure>\n\n

Does Kepler have a central mountain complex? Looking carefully at the region where the central mountains should appear reveals what are probably best described as central hills or mounds. Rising to a height of around 200m they aren\u2019t that impressive. To see them at their best, it\u2019s a good idea to choose a time when the lighting is oblique: the shadows they cast then gives them a good presence \u2013 perhaps more than they deserve. <\/p>\n\n

The streaks that cross the areas surrounding Kepler are fascinating. Kepler makes up the the right angle corner in an approximate right-angled triangle formed with Copernicus, 540km to the east, and Aristarchus, 550km to the north-northwest, both ray craters in their own right and great features for comparison. Kepler\u2019s rays appear to stop abruptly at a north-south boundary to the east, but flow a great distance to the north and west, less so to the south. A long and well-defined example heads directly west of Kepler\u2019s rim, but it\u2019s noted that extending this back through Kepler and to the east will bring you directly to Copernicus. Is this ray purely from the Kepler impact or is it augmented by the ejecta rays that emanate from Copernicus? Possibly, but there are long examples of Kepler rays not in line with Copernicus as well. <\/p>\n\n

Kepler\u2019s youthful age has allowed it to feature on the lunar surface unhindered with no incursions from other similar features. Its nearest neighbours are: 7km Kepler F, 32km to the west (centre-to-centre); the quintessentially bowl-shaped 11km Kepler A, which sits 65km to the southeast of Kepler; and 7km Kepler B, 81km to the east. The ancient, flat-floored form of 30km Encke is the largest nearby crater, located 115km to the south-southeast. Encke is an interesting crater to compare with Kepler. Its rim is irregular in shape but still sharp, despite an age estimated at more than 3.2 billion years. Its floor is fairly level but filled with concentric ridges and furrows. <\/p>\n\n

Although you\u2019ll get the most detail from Kepler at times of low Sun angle when the lighting is oblique, the bright nature of the crater\u2019s ejecta and relative darkness of the surrounding Oceanus Procellarum and Mare Insularum to the east, means that Kepler also stands out well during the direct illumination you get around full Moon. <\/p>\n\n

<\/p>\n\n

Photos: PETE LAWRENCE <\/p>\n","protected":false},"excerpt":{"rendered":"

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