M51 Supernova update. The supernova in the Whirlpool Galaxy (M51) peaked at magnitude 12.6 and is now dimming. It was magnitude 13.0 as of June 28th. That still makes it detectable in a lot of amateur telescopes, what with the sky being moonless early in the week, but don't delay; this is probably your last chance.
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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 Sky Atlas 2000.0 (stars to magnitude 8.5); and the even larger and deeper 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 Sky Atlas 2000.0 Companion by Strong and Sinnott, or the more detailed and descriptive 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) can be spotted very low in the west-northwest in twilight. Don't confuse it with Regulus far to its upper left.
Venus (magnitude –3.9) shines barely above the east-northeast horizon as dawn grows bright. Look for it about 15 or 20 minutes before sunrise if the air is very clear.
Mars (magnitude +1.4, in Taurus) is low in east-northeast in early dawn. Look for it very far lower left of Jupiter. Below or lower right of Mars is Aldebaran, similar in brightness and color.
Jupiter (magnitude –2.3, in southern Aries) rises around 2 a.m. and shines prominently in the east by dawn.
Saturn (magnitude +0.9, in Virgo) is southwest after dusk and getting lower. Shining 14° left of it is similar Spica. And 2/3° to Saturn's right is fainter Porrima (Gamma Virginis).
In a telescope, Saturn's rings are 7.6° from edge on. The rings are casting a their shadow southward onto the globe as a thin black line. The globe's shadow on the rings is just off the globe's celestial east (following) side. The North Equatorial Belt is a dusky band. North of it, signs of Saturn's seven-months-old white outbreak are still apparent in good images.
Uranus (magnitude 5.9, in western Pisces) and Neptune (magnitude 7.9, in Aquarius) are about equally high now before the very first light of dawn, in the southeast and south, respectively.
Pluto (magnitude 14.0, in Sagittarius) is highest in the south around midnight or 1 a.m. A big finder chart for it is in the July Sky & Telescope, page 64.
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.
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