Some daily events in the changing sky for July 17 – 25.
Friday, July 17
Saturday, July 18
Sunday, July 19
Monday, July 20
Tuesday, July 21
Wednesday, July 22
Thursday, July 23
Friday, July 24
Saturday, July 25
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 a telescope mount that is less than rigid and 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 deep in the glow of sunset.
Venus and Mars (magnitudes –4.1 and +1.1, respectively) are in the east during dawn. Venus is a dazzler; Mars, to Venus's upper right, is 120 times fainter. They're moving farther apart: from 10° to 13° separation this week.
Aldebaran, similar to Mars in both brightness and color, twinkles to the right of the line between the two planets. Above Mars are the Pleiades. Far left of the whole group shines bright Capella.
Jupiter (magnitude –2.8, in Capricornus) rises by the end of twilight and shines highest in the south in the early-morning hours.
Impact on Jupiter! A black dust scar like those of the Comet Shoemaker-Levy 9 impacts in 1994 has suddenly appeared in Jupiter's south polar region. See our article.
Saturn (magnitude +1.1, in Leo) is getting low in the west after dusk. Look early! In a telescope Saturn's rings are narrowing, appearing only 2½° from edge on. And they're getting very dim. The rings will turn edge-on to the Sun and go black on August 10th. They'll turn edge-on to Earth on September 4th, but by then Saturn will be lost in the sunset.
Uranus (magnitude 5.8, in Pisces), is high in the south before dawn.
Neptune (magnitude 7.8, in Capricornus) remains only about 1° from Jupiter — but it's 17,000 times fainter, as shown here. See our finder charts for Uranus and Neptune, good for the rest of this year.
Both of these outermost planets show a very pale blue-green tint in a medium-size to large telescope, if your eye is particularly sensitive to color. Otherwise, or in a smaller telescope, they're basically gray.
Pluto (14th magnitude, in northwestern Sagittarius) is at its highest in the south during evening. If you've got a big scope and a dark sky, you can take on the Pluto challenge using the finder chart in the June Sky & Telescope, page 53.
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.
"Science is built up of facts, as a house is with stones. But a collection of facts is no more a science than a heap of stones is a house."
— Henri Poincaré (1854–1912)
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