{"id":643251,"date":"2026-08-18T08:51:17","date_gmt":"2026-08-18T08:51:17","guid":{"rendered":"https:\/\/www.europesays.com\/ie\/643251\/"},"modified":"2026-08-18T08:51:17","modified_gmt":"2026-08-18T08:51:17","slug":"the-sky-today-on-tuesday-august-18-stars-and-sparklers","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/ie\/643251\/","title":{"rendered":"The Sky Today on\u00a0Tuesday, August 18: Stars and sparklers"},"content":{"rendered":"

\t\t\tBack to Article List\t\t<\/p>\n

\n\t\t\t\tLate tonight, moonless skies offer great deep-sky observer. Try for open cluster NGC 6939, neighbor to the famous Fireworks Galaxy.\t\t\t<\/p>\n

<\/p>\n

\t\t\t\t\"A<\/p>\n

\t\t\t\t\t\tOpen cluster NGC 6939 (upper left) in Cepheus lies close to the Fireworks Galaxy, a lovely face-on spiral galaxy known for its many supernovae. Credit: Ram Viswanathan (Flickr, CC BY-NC 2.0)<\/a>\t\t\t\t\t<\/p>\n

Looking for a sky event this week? Check out our full\u00a0Sky This Week<\/a>\u00a0column.\u00a0<\/strong><\/p>\n

August 17: Mars at Gemini\u2019s feet<\/a><\/strong><\/p>\n

Wait until after about 10 P.M. tonight to begin your deep-sky observing and the Moon won\u2019t be a bother. An excellent target is NGC 6939, an open cluster in Cepheus the King. This cluster is quite compact, about 8\u2019 across, and shines at 8th magnitude. You can locate it in the north late tonight \u2014 by 10 P.M. local daylight time, it is some 60\u00b0 high, to the upper left of Alderamin, Cepheus\u2019 alpha star. From this magnitude 2.5 sun, slide just under 6\u00b0 southwest to land on the cluster.\u00a0<\/p>\n

Although NGC 6939 is an open cluster and these groups are young, it\u2019s one of our galaxy\u2019s older such clusters, at some 1 billion to 2 billion years old. It can be viewed in binoculars, but larger apertures will pull out its stars as points, rather than simply showing a dim, amorphous glow.\u00a0<\/p>\n

NGC 6939 also has a famous neighbor \u2014 some \u2154\u00b0 to its southeast (and 2.1\u00b0 southwest of magnitude 3.4 Eta [\u03b7] Cephei) is NGC 6946, a face-on spiral known as the Fireworks Galaxy. Glowing at magnitude 8.9, this galaxy has had at least 10 supernovae pop off within it over the last century! Compare that with our own galaxy, which sees about one every century.\u00a0<\/p>\n

Spanning roughly 10\u2019, NGC 6946 can be a bit challenging because its light is spread out over a relatively large area, making it appear dim. It\u2019s also located behind a swath of light-absorbing dust within our own galaxy. Even so, it can be found in binoculars and it will show up as a faint, relatively detail-less glow in smaller scopes. In larger telescopes (11 inches), the brighter core and fainter arms become distinct, and grow even more detailed as you scale up your aperture.\u00a0<\/p>\n

Both objects show up well in astrophotos, making this a popular pair for imagers to target.<\/p>\n

Sunrise:<\/strong> 6:14 A.M.
Sunset:<\/strong> 7:53 P.M.
Moonrise:<\/strong> 12:47 P.M.
Moonset:<\/strong> 10:38 P.M.
Moon Phase:<\/strong> Waxing crescent (41%)
*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.\u00a0<\/p>\n

If you\u2019re willing to stay up late, you\u2019re in luck: NGC 7293, the Helix Nebula, is highest around 1 A.M. local daylight time on August 19, when it stands some 30\u00b0 above the southern horizon. It is also cataloged as Caldwell 63.<\/p>\n

\"A<\/p>\n

\t\tThe Helix Nebula is a lovely ring-shaped planetary in the constellation Aquarius, visible after moonset on August 19. Credit: Stephen Rahn (Flickr, CC0 1.0)<\/a><\/p>\n

Located in Aquarius, the Helix is a lovely circular planetary nebula generated as well as lit up by the dying star at its center. Although it is 8th magnitude \u2014 quite bright for a planetary \u2014 its inner portion covers some 16\u2019 of sky, making it one of the larger planetary nebulae we know. It also means that (like the Fireworks Galaxy yesterday) its light is spread out over a larger area, making its overall surface brightness low. But that doesn\u2019t mean it can\u2019t be seen \u2014 in fact, it can still be caught in binoculars or a small scope. On a very dark night (and if you have very good eyesight), you may even be able to see it without any optical aid! It\u2019s in a patch of sky in southwestern Aquarius devoid of bright stars, but you can hop some 7.8\u00b0 southwest of 3rd-magnitude Skat (Delta [\u03b4] Aquarii) to find it. For a fainter but closer signpost, use 5th-magnitude Upsilon (\u03c5) Aqr \u2014 it\u2019s just 1.2\u00b0 west of this star.\u00a0<\/p>\n

If you\u2019ve got a large scope, screw in a nebula filter to bring out more detail, including brightness variations along the edges of its ring.<\/p>\n

Alison Klesman<\/strong>\u00a0is senior editor of\u00a0Astronomy\u00a0magazine. She holds a Ph.D. in astronomy and has studied a variety of topics, from minor planets to supermassive black holes.<\/p>\n","protected":false},"excerpt":{"rendered":"Back to Article List Late tonight, moonless skies offer great deep-sky observer. Try for open cluster NGC 6939,…\n","protected":false},"author":2,"featured_media":643252,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_share_on_mastodon":"0"},"categories":[77],"tags":[18,19,17,2209,133,75779],"class_list":["post-643251","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-eire","tag-ie","tag-ireland","tag-observing","tag-science","tag-sky-tonight"],"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@ie\/117115663246856404","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/643251","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=643251"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/643251\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media\/643252"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media?parent=643251"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/categories?post=643251"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/tags?post=643251"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}