Zoom in on the Perseus Cluster<\/a><\/strong><\/p>\nIf you\u2019re up early today, try finding the famous Keystone of Hercules in the eastern sky, about 40\u00b0 high two hours before sunrise. Looking east, you\u2019ll see a bright star (magnitude 0.0) some 20\u00b0 high at that time \u2014 that\u2019s Vega, the alpha star of Lyra the Lyre.\u00a0<\/p>\n
From here, glance to the upper right for a rough square of four stars located about \u2153 of the way from Vega to the bright star Arcturus (magnitude \u20130.1) in Bo\u00f6tes the Herdsman. That\u2019s the Keystone. Its brightest star is magnitude 2.8 Zeta (\u03b6) Herculis, which anchors the southwestern corner (the star farthest right as the constellation rises, at the upper righthand corner of the Keystone). To its upper right in the sky this morning is Eta (\u03b7) Her (magnitude 3.5), about 7\u00b0 to Zeta\u2019s north and forming the upper lefthand corner of the Keystone in this configuration. Then drop 6.5\u00b0 southeast (to the lower left) to Pi (\u03c0) Her (magnitude 3.2), and finally slide another 6.5\u00b0 southwest (to the lower right) to find magnitude 3.9 Epsilon (\u03b5) Her at the lower right corner of the box.<\/p>\n
If you have a telescope, take a moment to glance about \u2153 of the way along a line from Eta to Zeta Her \u2014 there you\u2019ll find the famous Hercules Cluster (M13), a magnificent globular cluster glowing at 6th magnitude.\u00a0<\/p>\n
Sunrise:<\/strong>\u00a07:22 A.M.
Sunset:<\/strong>\u00a04:53 P.M.
Moonrise:<\/strong>\u00a0\u2014
Moonset:<\/strong>\u00a010:51 A.M. \u00a0
Moon Phase:<\/strong>\u00a0Waning gibbous (55%)
*Times for sunrise, sunset, moonrise, and moonset are given in local time from 40\u00b0 N 90\u00b0 W. The Moon\u2019s illumination is given at 10 P.M. local time from the same location.<\/p>\nJupiter reaches opposition the morning of January 10 at 4 A.M. EST. As the clock ticks over from midnight on the 9th to the early hours of the 10th, the gas giant is high in the southern sky, some 70\u00b0 above the horizon and located to the lower right of Pollux in Gemini. Turn a telescope on the planet and you\u2019ll see that by 12:30 A.M. CST (early on the 10th for the eastern half of the U.S.; still late on the 9th for the Mountain and Pacific time zones), Callisto is closing in on Jupiter\u2019s southeastern limb. Europa is farther east, while Io (closer) and Ganymede lie to the gas giant\u2019s west.\u00a0<\/p>\n
Callisto reaches the limb and begins to transit just minutes before 2 A.M. EST on the 10th (11 p.m. PST on the 9th in this time zone only). Within 10 minutes, it\u2019s passed fully in front of the planet, moving from east to west. Two hours later, around 4 A.M. EST, Callisto is roughly central on the disk.\u00a0<\/p>\n
![\"Callisto](\"https:\/\/www.europesays.com\/ie\/wp-content\/uploads\/2026\/01\/ASY-SM0126_06.png\")
<\/p>\n
\t\tThe day Jupiter reaches opposition, Callisto nearly blends with its shadow as they transit. Can you spot the shadow, just peeking out from Callisto\u2019s southern edge? Credit: Astronomy: Roen Kelly<\/p>\n
At opposition, the Sun appears directly behind us as we look at Jupiter and from a viewpoint above the solar system, Earth stands directly between the Sun and the gas giant. That means as moons cross Jupiter on this date only, they directly overlap their shadows. With Callisto central on the disk, look closely at the moon\u2019s southern edge. Does this limb appear slightly darker or distended? This may be all the evidence of its shadow, also crossing the cloud tops at the same time, that you may see. You\u2019ve got plenty of time to hunt for (or even try to photograph) it \u2014 Callisto\u2019s transit ends shortly after 6 A.M. EST on January 10, roughly an hour before sunrise on the East Coast.\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"Back to Article List This famous asterism at the heart of the Strongman is visible in the early-morning…\n","protected":false},"author":2,"featured_media":275857,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[77],"tags":[18,19,17,2209,133,75779],"class_list":{"0":"post-275856","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-eire","9":"tag-ie","10":"tag-ireland","11":"tag-observing","12":"tag-science","13":"tag-sky-tonight"},"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@ie\/115865022975457035","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/275856","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/comments?post=275856"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/275856\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media\/275857"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media?parent=275856"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/categories?post=275856"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/tags?post=275856"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
![\"\"\/](\"https:\/\/www.europesays.com\/ie\/wp-content\/uploads\/2026\/01\/Keystone.png\")
<\/p>\n