Some daily events in the changing sky for July 27 August 4.
Friday, July 27
Saturday, July 28
Sunday, July 29
Monday, July 30
Tuesday, July 31
Wednesday, August 1
Thursday, August 2
Friday, August 3
Saturday, August 4
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 foldout 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 maps; the standard is Sky Atlas 2000.0) and good deep-sky guidebooks (such as Sky Atlas 2000.0 Companion or the enchanting though dated Burnham's Celestial Handbook). Read here how to use them most effectively.
More beginners' tips: "How to Start Right in Astronomy".
This Week's Planet Roundup
Mercury, brightening from magnitude 0 to 1, is having a fine apparition low in the glow of dawn. Look for it above the east-northeast horizon about 45 to 60 minutes before sunrise, very far below Capella. Nearby are fainter Pollux and Castor, as shown at the top of this page. Bring binoculars to look for them. (To find your local sunrise time, and much else, make sure you've 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.)
Venus (magnitude 4.3) is fast disappearing into the glare of sunset.
Mars (magnitude +0.5, in Taurus) rises around 1 a.m. daylight saving time is and high in the east by dawn. Look for the Pleiades to its left, and Mars-like Aldebaran below the Pleiades.
In a telescope Mars is currently only 7 arcseconds in diameter, but it's on its way to a Christmas-season opposition, when it will grow to nearly 16 arcseconds wide in the evening sky. This will be a far cry from the 25" width it displayed at its record-breaking close approach in 2003 but it'll be the largest Mars will appear again until the opposition of 2016!
Incidentally, if friends or family tell you they hear that Mars will become as big and bright as the full Moon in the next few weeks, be nice to them. Read our article about the regular-as-clockwork August Mars Hoax, so that you can tell them the whole story. (My comment about immunization is optional.)
Jupiter (magnitude 2.5, in southern Ophiuchus) glares in the south during twilight and lower in the southwest later after dark. Antares, less bright, sparkles redly 5° below it; the two are evening companions all summer. Other stars of Scorpius shine below them and to their right.
Saturn is lost in the sunset.
Uranus (magnitude 5.8, in Aquarius) and Neptune (magnitude 7.8, in Capricornus) are well up in the south during early morning hours.
Pluto (magnitude 13.9, in the northwestern corner of Sagittarius) is highest right after dark, 18° east-northeast of Jupiter. Finder charts for Uranus, Neptune, and Pluto are in the July Sky & Telescope, page 60.
All descriptions that relate to your horizon including the words up, down, right, and left are written for the world's midnorthern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America. Eastern Daylight Time (EDT) equals Universal Time (UT, UTC, or GMT) minus 4 hours.
To always get the up-to-date Sky at a Glance, bookmark this URL:
"Rational and innocent entertainment of the highest kind."
John Mills, 19th century Scottish manufacturer and founder of Mills Observatory, on amateur astronomy.