Sky at a Glance | October 5th, 2007

Some daily events in the changing sky for October 5 – 13.

Looking east at dawn
Venus, Saturn, and Regulus perform a three-way tango in the early dawn this week. And on Sunday morning October 7th, the waning crescent Moon shines smack in their midst! This one's worth setting your alarm clock and going out with your telescope. Start observing a good 90 minutes before sunrise. (To find your local sunrise time, 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.)
Sky & Telescope diagram

Friday, October 5

  • Before and during dawn Saturday morning, the waning Moon hangs above the bunch-up of Venus, Saturn, and Regulus (above the top of the frame at right).

    Saturday, October 6

  • Early Sunday morning, the waning crescent Moon shines right amid bright Venus and fainter Saturn and Regulus, as shown at right. The Moon will occult Regulus before dawn for western Europe.

    Sunday, October 7

  • The red long-period variable star R Draconis should be at maximum light (7th or 8th magnitude) around now.

    Monday, October 8

  • After dark, look for Fomalhaut, the first-magnitude Autumn Star, making its lonely appearance low in the southeast. It's highest in the south around 10 or 11 p.m. (daylight saving time).

    Tuesday, October 9

  • Venus, Saturn, and Regulus appear closest together in the dawn on Wednesday morning. They'll fit in a circle 4.5° wide. This is much wider than the field of view you see in most telescopes even at their lowest power, but it's a little smaller than the field of most binoculars.

    Wednesday, October 10

  • Face west after dark this week and look very high, almost overhead. The brightest star there is Vega, 25 light-years away. The brightest star even closer to the zenith is Deneb, about 1,500 light-years distant. The third star of the big "Summer Triangle" is Altair, less high in the south to southwest. It's only 17 light-years from Earth.

    Thursday, October 11

  • New Moon (exact at 1:01 a.m. EDT).

    Friday, October 12

  • By late evening in October, the landmark W shape of the constellation Cassiopeia is exactly balancing on one end high in the northeast, while the Big Dipper lies exactly horizontally just above the north-northwest horizon (or below the horizon if you're as far south as Tampa or Houston).

    Saturday, October 13

  • A twilight challenge: If the sky is very clear about 15 or 20 minutes after sunset, use binoculars to scan low above the west-southwest horizon for the very thin crescent Moon — and tiny little Mercury about two Moon-diameters south (lower left) of it. This applies to North America; their relative positions are different after sunset elsewhere. Good luck.

    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 by Strong and Sinnott, the even more detailed Night Sky Observer's Guide by Kepple and Sanner, or the enchanting though somewhat dated Burnham's Celestial Handbook). Read how to use them effectively.

    More beginners' tips: "How to Start Right in Astronomy".

    This Week's Planet Roundup

    Venus on Sept. 25. 2007
    Venus is becoming a thicker crescent in a telescope as it climbs higher up away from the Sun in the morning sky. Sean Walker made this image from red, green, blue, and ultraviolet video stacks on the morning of September 25, 2007. Click image for separate RGB and ultraviolet views.
    S&T: Sean Walker
    Mercury (about magnitude +0.5) is very deep in the glow of sunset and fading now. Early in the week, try looking for it with binoculars about 20 minutes after sundown just above the west-southwest horizon. Good luck.

    Venus (magnitude –4.7, in Leo) blazes high in the east before and during dawn. Near it are Saturn and Regulus — and on the mornings of the 6th and 7th, so is the crescent Moon. A telescope shows that Venus itself is a crescent, thickening from week to week even as the planet shrinks into the distance.

    Mars (magnitude –0.2, in the feet of Gemini) rises around 10 p.m. daylight saving time and shines very high toward the south at dawn — near the zenith, in fact, for mid-northern observers. Compare Mars's fiery color with that of Betelgeuse — which is off to its right or lower right after they rise, and below it in early dawn.

    Sean Walker
    In a telescope, Mars appears gibbous and 10 to 10.5 arcseconds in diameter. It will reach 16" diameter around its Christmas-season opposition. The Martian dust storms of July and August have abated, and while the planet's atmosphere is still bright and hazy with dust, surface features are showing through somewhat better. But they're still low-contrast.

    Jupiter (magnitude –2.0, in southern Ophiuchus) glares in the southwest during and after twilight. It sets by midevening. Antares, much less bright, sparkles redly 7° or 8° below it.

    Saturn (magnitude +0.7) is the brightest "star" near dazzling Venus in the dawn. Fainter Regulus (magnitude +1.4) is right there too; it's upper right of Saturn.

    Uranus (magnitude 5.8, in Aquarius) and Neptune (magnitude 7.9, in Capricornus) are well placed in the southeast to south during evening. Finder charts for them are in the July Sky & Telescope, page 60, and online. With a big scope you can shoot for their faint moons! See the October Sky & Telescope, page 69.

    Pluto (magnitude 14.0, in Sagittarius) is sinking in the southwest at dusk.

    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.

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