Some daily events in the changing sky for September 11 19.
Friday, Sept. 11
Jupiter's moon Io reappears out of eclipse just off the planet's eastern limb at 10:53 p.m. EDT. Later Europa reappears out of eclipse, at 1:12 a.m. EDT.
Saturday, Sept. 12
You can always find your local sunrise and start-of-dawn times, and much else, once you put your location into our online almanac. (If you're on daylight saving time like most of North America, make sure the Daylight Saving Time box is checked.)
Sunday, Sept. 13
For a timetable of Jupiter's satellite phenomena throughout September, good worldwide, see the September Sky & Telescope, page 56.
Monday, Sept. 14
For a complete list of such mutual events among Jupiter's satellites through the end of the year that are visible from North America, see the October Sky & Telescope, page 56.
Wednesday, Sept. 16
Thursday, Sept. 17
Friday, Sept. 18
Saturday, Sept. 19
Want to become a better amateur astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope. For an easy-to-use constellation guide covering the whole evening sky, use the big monthly map in each issue of Sky & Telescope, the essential magazine of astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).
Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts; the standards are Sky Atlas 2000.0 or the smaller Pocket Sky Atlas) and good deep-sky guidebooks (such as Sky Atlas 2000.0 Companion by Strong and Sinnott, the more detailed and descriptive Night Sky Observer's Guide by Kepple and Sanner, or the classic Burnham's Celestial Handbook). Read how to use them effectively.
Can a computerized telescope take their place? I don't think so not for beginners, anyway, and especially not on mounts that are less than top-quality mechanically. As Terence Dickinson and Alan Dyer say in their Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand and a curious mind." Without these, "the sky never becomes a friendly place."
More beginners' tips: "How to Start Right in Astronomy".
This Week's Planet Roundup
Mercury is hidden in the glare of the Sun.
Venus (magnitude 3.9, in Leo) shines low in the east before and during dawn. Look for Regulus, much fainter, below it. Regulus climbs closer to Venus each morning; they'll have a close conjunction on the 20th.
Mars (magnitude +0.9, in Gemini) rises around 1 a.m. and is high in the east before dawn. In a telescope it's still only 6 arcseconds wide: a tiny, fuzzy blob, though noticeably gibbous. Mars is on its way to an unremarkable opposition late next January, when it will grow no larger than 14 arcseconds wide.
Jupiter (magnitude 2.8, in Capricornus) comes into view in the southeast as twilight fades the first "star" to appear after sunset. It's higher in better telescopic view by 9 or 10 p.m. Jupiter shows more observable apparent surface area (square arcseconds) than all the other planets combined.
July's impact mark on the planet has faded from view; see our article.
Saturn is hidden behind the glare of the Sun.
Uranus (magnitude 5.7, just below the Circlet of Pisces) is well up in the southeast by 10 p.m.
Neptune (magnitude 7.8, in Capricornus) appears 6° east of Jupiter and nearly 20,000 times fainter. See our finder charts for Uranus and Neptune.
Near Uranus is the asteroid 3 Juno, now close to opposition at magnitude 7.6. This is the brightest Juno will become until 2018! See the chart in the September Sky & Telescope, page 55.
Pluto (14th magnitude, in northwestern Sagittarius) is still well up in the south-southwest right after dark. See the finder chart in the June Sky & Telescope, page 53. Good luck.
All descriptions that relate to your horizon or zenith including the words up, down, right, and left are written for the world's mid-northern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America. Eastern Daylight Time (EDT) equals Universal Time (also known as UT, UTC, or GMT) minus 4 hours.
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