This Week's Sky at a Glance
Some daily events in the changing sky for October 21 29
Friday, Oct. 21
Saturday, Oct. 22
Sunday, Oct. 23
Monday, Oct. 24
Tuesday, Oct. 25
Wednesday, Oct. 26
Thursday, Oct. 27
Then at 11:37 p.m. EDT, Ganymede disappears into eclipse by Jupiter's own shadow, just a hairsbreadth beyond Jupiter's western limb.
Friday, Oct. 28
Saturday, Oct. 29
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 the center of 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 must have a detailed, large-scale sky atlas (set of charts). The standards are the Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger and deeper Sky Atlas 2000.0 (stars to magnitude 8.5); and the even larger Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts effectively.
You'll also want a good deep-sky guidebook, such as Sue French's new Deep-Sky Wonders collection (which includes its own charts), Sky Atlas 2000.0 Companion by Strong and Sinnott, the bigger Night Sky Observer's Guide by Kepple and Sanner, or the classic if dated Burnham's Celestial Handbook.
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."
This Week's Planet Roundup
Mercury (about magnitude 0.3) is deep in the sunset below much-brighter Venus. If the air is very clear, use binoculars or a telescope about 15 or 20 minutes after sundown this week to see if you can pick up Mercury 3° lower right of Venus early in the week, and 2° below Venus later in the week.
Venus (magnitude 3.8) is a little above the west-southwest horizon 20 or 30 minutes after sunset. It's getting less difficult to spot every week.
Mars (magnitude +1.2, in Leo) rises around 1 or 2 a.m. daylight-saving time. By the beginning of dawn it's in good view high in the east-southeast. Mars is closing in on similarly bright Regulus below it. They're 10° apart on October 22nd and 7° apart on the 29th. In a telescope Mars is a tiny blob only 5.7 arcseconds wide.
. Jupiter (magnitude 2.9, in southern Aries) shines low in the east-northeast in twilight, then blazes higher in the east to southeast all evening. Look above it for the stars of Aries and below it for the head of Cetus, rather dim. Jupiter is nearly at its highest in the south by midnight. It's a big 49 arcseconds wide, as big as it will appear at its October 28th opposition.
Moreover, this is an unusually close Jupiter opposition. Last year Jupiter came closer to Earth than it had since 1963. This year it's only an insignificant 0.4% farther. See our guide to observing Jupiter with a telescope.
Saturn is deep in the glow of sunrise.
Uranus (magnitude 5.7, in Pisces) and Neptune (magnitude 7.9, in Aquarius) are well placed in the south and southeast by mid-evening. Use our printable finder chart for both, or see the September Sky & Telescope, page 53.
All descriptions that relate to your horizon 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.
NEW BOOK: Sue French's DEEP-SKY WONDERS! This big, long-awaited observing guide by Sky & Telescope's Sue French is now available from Shop at Sky. Hefty and lavishly illustrated, it contains Sue’s 100 favorite sky tours (25 per season), with finder charts, from her 11 years of writing the Celestial Sampler and Deep-Sky Wonders columns for S&T. Don’t miss it!
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