{"id":35267,"date":"2022-08-11T00:00:00","date_gmt":"2022-08-11T00:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/?post_type=purple_issue&p=35267"},"modified":"2022-09-12T11:14:09","modified_gmt":"2022-09-12T11:14:09","slug":"the-big-three-12","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/2022\/08\/11\/the-big-three-12\/","title":{"rendered":"The big three"},"content":{"rendered":"\n

The top sights to observe or image this month <\/span><\/p>\n\n

DON’T MISS: Lunar occultation of Uranus <\/h5>\n\n

BEST TIME TO SEE: <\/strong>14 September, 21:30 BST (20:30 UT) until 23:30 BST (22:30 UT) <\/p>\n\n

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

The Moon will appear to pass in front of the planet Uranus on 14 September, an event known as a lunar occultation. Lunar occultations of faint stars are common, but seeing the Moon move in front of a bright star is relatively infrequent. Seeing the Moon pass in front of a planet is quite a rare event. <\/p>\n\n

On 14 September, the Moon will be at 77%-lit waning gibbous phase. Uranus, shining at mag. +5.7 will require binoculars or a telescope to see properly. Locate the planet at 21:30 BST (20:30 UT) and familiarise yourself with where Uranus is positioned relative to the Moon\u2019s disc. At this time, the separation between Uranus and the eastern edge of the Moon (confusingly, the Moon\u2019s western limb) will be around one apparent lunar diameter. <\/p>\n\n

There\u2019s nothing else of a similar brightness nearby, so identifying Uranus shouldn\u2019t be too hard. Once you\u2019ve located it, there\u2019s nothing more to do than wait. <\/p>\n\n

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It will take around eight seconds for Uranus to disappear behind the Moon\u2019s leading, bright limb as occultation begins <\/figcaption><\/figure>\n\n\n\n

<\/p>\n<\/div>\n\n\n\n

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After disappearing for 50 minutes, its return from behind the Moon\u2019s following, dark limb will also take eight seconds <\/figcaption><\/figure>\n\n\n\n

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The Moon\u2019s bright limb slowly approaches Uranus until first contact, the time of which varies slightly with location. It\u2019s recommended to keep watching the planet when the Moon is close. From the centre of the UK, Uranus will make contact with the Moon\u2019s eastern edge (western limb) at 22:30 BST (21:30 UT).<\/span><\/p>\n\n

Uranus has an apparent diameter of 3.7 arcseconds and will take around eight seconds to fully disappear. Atmospheric seeing will have a big effect here, the tiny planetary disc being heavily influenced by Earth\u2019s unstable atmosphere. <\/p>\n\n

Uranus remains hidden for around 50 minutes, the planet reappearing at 23:21 BST (22:21 UT) from behind the Moon\u2019s dark western edge (eastern limb). The period of time Uranus is hidden will also vary slightly with location, so observe the Moon\u2019s dark edge earlier than the expected reappearance, say from 23:10<\/span> BST (22:10 UT). Again, Uranus should take around eight seconds to be fully revealed as the Moon moves east.<\/span><\/p>\n\n

A telescope setup showing the entire Moon\u2019s disc guarantees a view of the reappearance, although it\u2019ll be hard to see Uranus as anything more than a dot. More magnification will show the planet as a disc, but this increases the possibility of missing the reappearance. If you have an accurate, polar-aligned mount, centring on Uranus at high magnification and sticking with it as the Moon performs the occultation is the best way to guarantee a high-powered view. <\/p>\n\n

Thin Moon spotting with Venus <\/h4>\n\n

BEST TIME TO SEE: <\/strong>25 September, from 40 minutes before sunrise (stop viewing at sunrise) <\/p>\n\n

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Try to spot the ultra-thin Moon in the east before sunrise on 25 September. Moon\u2019s size exaggerated for clarity <\/figcaption><\/figure><\/div>\n\n

When the Moon is presented against a truly dark sky, it\u2019s easy to locate as it dominates the view. When it\u2019s in the daytime sky, it\u2019s less easy to see due to lower contrast, but the thicker phases can still stand out pretty well. <\/p>\n\n

When the Moon appears in the daytime sky or twilight periods with a phase less than 2% it becomes significantly trickier to pick out. When it\u2019s presented with a phase less than 1% it\u2019s downright difficult! <\/p>\n\n

This will be the case on the morning of 25 September: a 0.6%-lit waning crescent Moon situated 8\u02da from the Sun. This is an interesting arrangement for several reasons. The ecliptic makes a steep angle with the eastern horizon at this time of year before sunrise. This means that the Moon, which never moves that far from the ecliptic, will be optimally placed above the horizon before sunrise. In addition, there\u2019s a theoretical limit as to how far a Moon can be from the Sun before it becomes invisible. This value is known as the Danjon limit and is usually quoted as about 7\u02da. The morning Moon on 25 September is perilously close to this value, with an actual separation value of 7.9\u02da from the Sun.<\/span><\/p>\n\n

But best of all, if you go looking for this particular Moon, you\u2019ll have a guide in the form of the brilliant planet Venus. If you have a clear view looking towards the eastern horizon on the morning of 25 September, point your binoculars at Venus and in the same field of view, just to the left and up a bit from the planet, there will be that ultra-thin lunar crescent. If you look but can\u2019t see it, look again removing all preconceptions of how you think the crescent should look. It will be extremely delicate and very tricky to see. Be sure to stop looking before the Sun rises.<\/span><\/p>\n\n

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CAUTION <\/span><\/strong><\/h4>\n\n\n\n

Only attempt to find Venus and the Moon when the Sun is below the horizon <\/p>\n<\/div><\/section>\n\n

<\/div>
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Harvest Moon 2022 <\/h4>\n\n\n\n

BEST TIME TO SEE: <\/strong>Moonrise on 8\u201312 September and 7\u201311 October <\/p>\n\n\n\n

The Moon is full at 11:00 BST (10:00 UT) on 10 September, the closest full Moon to the Northern Hemisphere\u2019s autumn equinox, which is at 02:03 BST (01:03 UT) on 23 September. This makes it the Harvest Moon for 2022. <\/p>\n\n\n\n

A Harvest Moon\u2019s proximity to the September equinox means that the rise times for the near-to-full phases of the Moon are nearly the same on the days before and after 10 September. It was the abundance of bright early-evening moonlight on those consecutive days that traditionally lit the fields for collecting the harvest. <\/p>\n\n\n\n

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Track the unusually similar moonrise times either side of the Harvest Moon <\/figcaption><\/figure>\n\n\n\n

It\u2019s an interesting exercise to note the rise time of the Moon on 8 September, then again on 9, 10, 11 and 12 September, calculating the differences. Waiting for the fuller phases of the Moon to rise is a great way to experience the visual effect of the Moon illusion, which makes these phases appear enormous when close to the horizon. The full Moon on 9 October is just a couple of days further away from the equinox than September\u2019s and you\u2019ll observe a similar pattern in the rise times for its fuller phases.<\/span><\/p>\n\n\n\n

The period close to the March equinox represents the opposite situation, with the difference between successive moonrises for the fuller phases of the Moon being the largest of the year. <\/p>\n<\/div><\/section>\n\n

<\/p>\n\n

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

The top sights to observe or image this month<\/p>\n","protected":false},"author":24,"featured_media":35262,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ub_ctt_via":"","purple_page_number":"46","purple_custom_meta_purple_page_number":"46","purple_seq_number":"1","purple_custom_meta_purple_seq_number":"1","purple_source_article":"article_46-1.xml","purple_custom_meta_purple_source_article":"article_46-1.xml","purple_source_issue":"September-2022","purple_custom_meta_purple_source_issue":"September-2022","purple_external_id":"September-2022-46-1","purple_custom_meta_purple_external_id":"September-2022-46-1","purple_issue_code":"|0000086556||","purple_custom_meta_purple_issue_code":"|0000086556||","purple_android_product":"com.im.skyatnight.208","purple_custom_meta_purple_android_product":"com.im.skyatnight.208","purple_ios_product":"com.im.skyatnight.208","purple_custom_meta_purple_ios_product":"com.im.skyatnight.208","purple_web_product":"","purple_custom_meta_purple_web_product":"","purple_publication_id":"075fab74-0a21-4201-866a-899d6c41c40c","purple_migrated":"","kt_blocks_editor_width":""},"categories":[22],"tags":[14],"featured_image_src":"https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/08\/fe4b53d4-aa7f-45c8-81c7-d872f1143c2b.jpg","author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"acf":{"readingTimeMinutes":"6","apple_news_title":""},"uagb_featured_image_src":{"full":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/08\/fe4b53d4-aa7f-45c8-81c7-d872f1143c2b.jpg",1566,1322,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/08\/fe4b53d4-aa7f-45c8-81c7-d872f1143c2b-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/08\/fe4b53d4-aa7f-45c8-81c7-d872f1143c2b-300x253.jpg",300,253,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/08\/fe4b53d4-aa7f-45c8-81c7-d872f1143c2b-768x648.jpg",768,648,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/08\/fe4b53d4-aa7f-45c8-81c7-d872f1143c2b-1024x864.jpg",800,675,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/08\/fe4b53d4-aa7f-45c8-81c7-d872f1143c2b-1536x1297.jpg",1536,1297,true],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/08\/fe4b53d4-aa7f-45c8-81c7-d872f1143c2b.jpg",1566,1322,false]},"uagb_author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"uagb_comment_info":0,"uagb_excerpt":"The top sights to observe or image this month","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/35267"}],"collection":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/users\/24"}],"replies":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/comments?post=35267"}],"version-history":[{"count":14,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/35267\/revisions"}],"predecessor-version":[{"id":36465,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/35267\/revisions\/36465"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media\/35262"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=35267"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=35267"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/tags?post=35267"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}