Sky at a Glance | July 8th, 2011

M51 Supernova update. The supernova in M51 (the Whirlpool Galaxy) has faded to about magnitude 13.6 as of July 7th, but its fading has slowed. It's still visible in large amateur telescopes although moonlight is becoming a problem; the earlier in the week you try for it the better.

Here's an up-to-date light curve from the AAVSO. See our original article with finder photo.


The view shortly after dark
On Friday evening, the Moon is just past first quarter.

Friday, July 8

  • Spica shines to the right of the Moon after dusk, with Saturn and Porrima farther right as shown here. Get your telescope on all these objects early; they move lower later in the evening.

    Saturday, July 9

  • Titan, the brightest satellite of Saturn, can be found in a telescope about four ring-lengths west of Saturn this evening and tomorrow evening. With an aperture of 6 inches or more, you may be able to make out Titan's orange tint due to its hydrocarbon-smogged atmosphere.

    Sunday, July 10

  • Arcturus is the brightest star very high in the west-southwest after dark. Vega is the brightest even higher in the east. A third of the way from Arcturus to Vega, look for the mostly dim semicircle of Corona Borealis, the Northern Crown. Two-thirds of the way, look for the dim Keystone of Hercules.

    Monday, July 11

  • Look 2° or 3° below the Moon for Antares early this evening, as shown below.

    Summer Moon in summer constellations
    The Moon crosses Scorpius and Sagittarius as it waxes to full. In these scenes, the Moon is always placed for an observer in the middle of North America. European skywatchers: move each Moon symbol a quarter of the way toward the one for the previous date. The Moon is shown three times its actual apparent diameter.

    Tuesday, July 12

  • Happy birthday Neptune! Today it's exactly one Neptune year since the planet's discovery in 1846. Never again will a major planet of the solar system have failed to complete a full orbit since it was found. See the July Sky & Telescope, page 28. To locate Neptune with your binoculars or telescope (at magnitude 7.9), you can use our printable finder chart.

    Wednesday, July 13

  • Look below the bright Moon for the Teapot pattern of Sagittarius, as shown above.

    Thursday, July 14

  • Full Moon tonight (exact at 2:40 a.m. Friday morning Eastern Daylight Time). The Moon is left of the Sagittarius Teapot after dark.

    The constellation Lyra
    The little constellation Lyra dangles below Vega these evenings. For much of the time, Beta Lyrae is almost exactly as bright as Gamma. However. . . .
    Akira Fujii
  • The eclipsing binary star Beta Lyrae is coming out of its minimum light at the time of nightfall for the Americas. See the June Sky & Telescope, page 60.

    Friday, July 15

  • After the just-past-full Moon rises well up late this evening, use binoculars to look a little above it for Beta Capricorni and, higher, the wide double star Alpha Capricorni. With good distance vision, you can normally split Alpha Cap naked-eye. Can you still do this with the bright Moon so close?

    Saturday, July 16

  • With summer almost a third of the way through, the Big Dipper is descending in the northwest after dark and starting to scoop to the right, dipper-wise, as if picking up water to dump over the world in the evening next spring.


    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).

    Pocket Sky Atlas
    The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6 — which may sound like a lot, but that's less than one star in an entire telescopic field of view, on average. By comparison, Sky Atlas 2000.0 plots 81,312 stars to magnitude 8.5, typically one or two stars per telescopic field. Both atlases include many hundreds of deep-sky targets — galaxies, star clusters, and nebulae — to hunt among the stars.
    Sky & Telescope

    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 (magnitude 0.0) remains very low in the west-northwest in twilight. Don't confuse it with Regulus well to its upper left. Mercury and Regulus will pass 3° apart on July 26th.

    Venus is disappearing deep into the glow of sunrise.

    Mars (magnitude +1.4, in Taurus) is moderately low in the east-northeast as dawn begins to brighten. Look for it very far lower left of bright Jupiter. To the right of Mars (by 6° to 10°: this week) is Aldebaran, similar in brightness and color.

    In a telescope Mars is still just a tiny blob only 4.3 arcseconds in diameter. It's on its way to a poor opposition (13.9 arcseconds wide) next March.

    Jupiter on June 8, 2011
    Jupiter is coming into better view now in the dawn, but it's still very far from its best. Christopher Go obtained this fine stacked-video image on June 8th. Jupiter's dark South Equatorial Belt (above center) has fully returned and is very wide. The narrower North Equatorial Belt remains darker red-brown, with even darker barges. At the time of the photo the Great Red Spot had just barely passed the planet's central meridian (where the System II longitude was 163°). The SEB practically encompasses the Red Spot, and the Red Spot Hollow around the spot has changed from white to dark. South is up.

    Jupiter (magnitude –2.3, in southern Aries) rises around 1 or 2 a.m. daylight saving time and shines high in the east by dawn.

    Saturn (magnitude +0.9, in Virgo) is southwest after dusk and sinking lower. Shining 14° left of it is similar, but bluer, Spica. And about 1° to Saturn's right is fainter Porrima (Gamma Virginis), still forming a striking pair with it.

    In a telescope, Saturn's rings are 7.6° from edge on. The rings are casting 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. Identify the Saturnian satellites visible in your telescope with our Saturn's moons tracker.

    Uranus (magnitude 5.9, in western Pisces) and Neptune (magnitude 7.9, in western Aquarius) are about equally high now before the very first light of dawn, in the southeast and south, respectively. Neptune is having its first birthday this week, at least from the human point of view; see July 12 above. Here's our printable finder chart for both planets.

    Pluto (magnitude 14.0, in northern Sagittarius) is highest in the south around midnight. 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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