{"id":43806,"date":"2023-04-18T14:13:18","date_gmt":"2023-04-18T14:13:18","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/?post_type=purple_issue&p=43806"},"modified":"2023-04-27T14:54:43","modified_gmt":"2023-04-27T14:54:43","slug":"the-big-three-20","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/2023\/04\/18\/the-big-three-20\/","title":{"rendered":"The big three"},"content":{"rendered":"\n

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

DON\u2019T MISS <\/span><\/strong><\/h5>\n\n

Lunar occultation of Jupiter<\/strong><\/span><\/h4>\n\n

BEST TIME TO SEE: <\/strong>17 May, from 11:30 BST (10:30 UT) through to 15:30 BST (14:30 UT)
RECOMMENDED EQUIPMENT:<\/strong> Binoculars or small\/medium telescope<\/p>\n\n

\"\"
17 May, start observing from 14:20 BST (13:20 UT). Moon\u2019s altitude approximately 35\u00b0 at this time, above the southwest horizon <\/figcaption><\/figure>\n\n

Lunar occultations of planets aren\u2019t very common at all. If you\u2019ve been following events over the past few months, you might question this statement seeing as there have been three recent lunar occultations of Uranus and one of Mars visible from the UK. However, delve back before the first event, the lunar occultation of Uranus on 14 September 2022, and there weren\u2019t any for several years before that. This month there\u2019s a very rare lunar occultation of Jupiter, an event which comes with a couple of catches. <\/p>\n\n

Jupiter is a morning planet currently, not particularly well-placed and rising just 50 minutes before the Sun, mid-month. As it pops up above the east-northeast horizon on the morning of 17 May, it will be accompanied by a slender, but quite visible 7%-lit waning crescent Moon. From the UK, the Moon will appear 5\u00b0 to the right of mag. \u20131.9 Jupiter. Fifty minutes later, the Sun will rise and, if the weather is kind, the sky will turn bright blue. <\/p>\n\n

At this point, you\u2019re probably anticipating the first catch: the occultation occurs during daylight hours from the UK. Having said this, it\u2019s still a perfectly feasible observation, although it will lack the spectacle of a nighttime lunar occultation of a bright Jupiter. <\/p>\n\n

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Location makes a big difference to what you\u2019ll actually see, producing either a close pass, graze or full occultation<\/figcaption><\/figure>\n\n

The Moon will be visible to the naked eye given cloud-free skies, but being a relatively thin crescent, it may need a bit of work to find. The pair are due south at 47\u00b0 altitude from central regions of the UK at 11:24 BST (10:24 UT) on 17 May. This is a good time to try for the Moon using a telescope on a driven equatorial mount. The Sun is only 27\u00b0 away though, so if you\u2019re using binoculars or the naked eye to locate the Moon, take care and do so in the shadow of a house, fence or some other opaque obstruction that leaves the region to the right of the Sun clear.<\/p>\n\n

At 14:30 BST (13:30 UT), Jupiter will appear like a ghostly echo of its nighttime self, close to the Moon\u2019s southern edge. Now for the second catch: the occultation can only be seen from the north of the UK, mostly from Northern Ireland and Scotland. Those living in the fuzzy \u2018graze zone\u2019 may see Jupiter partly occulted by the Moon\u2019s limb, his while those further south will witness a near miss.<\/p>\n\n

Approximate timings for various locations are shown on the map above, observing being recommended from 14:20 BST (13:20 UT) through to 15:20 BST (14:20 UT). <\/p>\n\n

<\/p>\n\n

\n\n

Venus at dichotomy <\/h4>\n\n

BEST TIME TO SEE: <\/strong>25 May\u201314 June
RECOMMENDED EQUIPMENT:<\/strong> Small\/medium telescope<\/p>\n\n

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Venus\u2019s changing appearance as it orbits; it\u2019s now approaching 50% lit (dichotomy) <\/figcaption><\/figure>\n\n

Venus is an inferior planet. This doesn\u2019t mean it\u2019s a lesser world than ours, it\u2019s simply a reference to the size of its orbit. Inferior planets have smaller orbits than Earth, superior planets larger orbits. Mercury and Venus are inferior planets, the rest are superior. <\/p>\n\n

Inferior planets are interesting to observe as their apparent sizes wax and wane noticeably over time and they show a full set of phases. Venus reaches greatest eastern elongation on 4 June, appearing 45.4\u00b0 to the east of the Sun and brilliant in the evening twilight. The planet should appear at 50% phase, known as dichotomy, on this date. <\/p>\n\n

The run up to dichotomy, say from 10 days before, is a good time to start making phase estimates and they\u2019re really easy to do. Simply observe Venus through the eyepiece, noting whether the planet\u2019s terminator is straight or curved. If straight, this is dichotomy. If curved, estimate how far across the diameter of Venus \u2013 at right angles to the terminator \u2013 the terminator extends. As an example, if the terminator stretched one-third across the diameter of Venus, this would be a 33% phase. <\/p>\n\n

Starting to observe early gives you more experience at making accurate assessments. It\u2019s easy to look and record \u201850%\u2019 at a first glance, but is it really 50% or perhaps a little above or below that? <\/p>\n\n

Why bother to do this? Surely the geometric position of Venus will give a precise and predictable value for its phase? Actually, this is not the case. The planet\u2019s thick atmosphere interferes with the apparent phase, giving rise to the \u2018phase anomaly\u2019, an effect that makes dichotomy appear earlier than it should when Venus is in the evening sky. How early? Well, that\u2019s up to you to find out! <\/p>\n\n

<\/p>\n\n

\n\n

2023\u2019s NLC season <\/h4>\n\n

BEST TIME TO SEE: <\/strong>Last week in May through to early August
RECOMMENDED EQUIPMENT:<\/strong> Binoculars<\/p>\n\n

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Watch out for these shimmering clouds at sunrise and sunset <\/figcaption><\/figure>\n\n

Noctilucent clouds (NLCs) are high-altitude ice-sheet clouds that form in the mesosphere at a height of around 82km. For the Northern Hemisphere, NLC season runs from late May through to early August and spotting their elusive displays is a popular pastime, helping to counter the frustration of the shorter nights. NLCs are seeded by fragmentary dust from meteor trails. Tiny ice crystals form around these particles when the mesosphere cools. Mesospheric cooling, rather counter-intuitively, occurs in each hemisphere\u2019s summer period. <\/p>\n\n

If present, NLCs are typically seen 90\u2013120 minutes after sunset, low above the northwest horizon, and a similar time before sunrise low above the northeast horizon. At such times, it\u2019s dark or at least deep-twilight dark for us on the ground, but the clouds appear to shine. The light is from the Sun; at the great height of an NLC cloud the Sun still appears above the horizon. <\/p>\n\n

NLCs often have an electric blue colour and exhibit fine, net-like structures. Appearing bright against a dark twilight sky, they are also very photogenic and may be bright enough to image with many models of smartphone camera. <\/p>\n\n

<\/p>\n\n

PICTURES: 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":43804,"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":"May-2023","purple_custom_meta_purple_source_issue":"May-2023","purple_external_id":"May-2023-46-1","purple_custom_meta_purple_external_id":"May-2023-46-1","purple_issue_code":"|0000086564||","purple_custom_meta_purple_issue_code":"|0000086564||","purple_android_product":"com.im.skyatnight.216","purple_custom_meta_purple_android_product":"com.im.skyatnight.216","purple_ios_product":"com.im.skyatnight.216","purple_custom_meta_purple_ios_product":"com.im.skyatnight.216","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\/2023\/04\/b6c6309d-6a87-472c-b3d5-cab88155044a.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\/2023\/04\/b6c6309d-6a87-472c-b3d5-cab88155044a.jpg",2048,603,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2023\/04\/b6c6309d-6a87-472c-b3d5-cab88155044a-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2023\/04\/b6c6309d-6a87-472c-b3d5-cab88155044a-300x88.jpg",300,88,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2023\/04\/b6c6309d-6a87-472c-b3d5-cab88155044a-768x226.jpg",768,226,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2023\/04\/b6c6309d-6a87-472c-b3d5-cab88155044a-1024x302.jpg",800,236,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2023\/04\/b6c6309d-6a87-472c-b3d5-cab88155044a-1536x452.jpg",1536,452,true],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2023\/04\/b6c6309d-6a87-472c-b3d5-cab88155044a.jpg",2048,603,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\/43806"}],"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=43806"}],"version-history":[{"count":3,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/43806\/revisions"}],"predecessor-version":[{"id":44317,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/43806\/revisions\/44317"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media\/43804"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=43806"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=43806"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/tags?post=43806"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}