Friday, Sept. 27
• Arcturus shines in the west as twilight fades out. Capella, equally bright, is barely rising in the north-northeast (depending on your latitude; the farther north you are the higher it will be.) They're both magnitude 0. Later in the evening, Arcturus and Capella shine at the same height in their respective compass directions.
When will this happen? That depends on both your latitude and longitude. When it does, turn to look southwest. There will be Jupiter at about the same height (depending on your latitude).
Look south-southeast, and there will be 1st-magnitude Fomalhaut about equally high too.
Saturday, Sept. 28
• The starry W of Cassiopeia stands high in the northeast after dark. The right-hand side of the W, the brightest side, is tilted up.
Look along the second segment of the W counting down from the top. Notice the dim naked-eye stars along that segment (not counting its two ends). The brightest of these, on the right, is Eta Cassiopeiae, magnitude 3.4. It's a Sun-like star just 19 light-years away with an orange-dwarf companion, a lovely binary in a telescope.
The "one" on the left, fainter, is a naked-eye pair in a dark sky: Upsilon1 and Upsilon2 Cassiopeiae, 0.3° apart. They're orange giants unrelated to each other, 200 and 400 light-years away. Upsilon1, slightly fainter, is the farther one.
• New Moon (exact at 2:26 p.m. Eastern Daylight Time).
Sunday, Sept. 29
• At this time of year the rich Cygnus Milky Way crosses the zenith soon after dark (for mid-northern latitudes). The Milky Way extends straight up from the southwest, like firelit smoke from some great dim campfire. It passes overhead, then runs straight down to the northeast — where it plummets through Cassiopeia, Perseus, and low Auriga.
• Algol in Perseus shines at its minimum brightness (magnitude 3.4 instead of its usual 2.3) for a couple hours centered on 12:34 a.m. tonight EDT, 9:34 p.m. PDT.
Monday, Sept. 30
• "My favorite observations allow me to make comparisons," writes Matt Wedel in the October Sky & Telescope: "similar objects at different distances, or objects of different sizes at the same distance." For binocular observers he offers some examples at the bowl of the Sagittarius Teaspoon, just above bright Saturn. See his Binocular Highlight column on page 43 of the October issue.
Tuesday, Oct. 1
• In the west, way left of the Big Dipper, shines bright Arcturus, the "Spring Star," a little lower at nightfall each week. From Arcturus, the narrow kite-shaped pattern of Bootes extends 24° to the upper right.
Wednesday, Oct. 2
• The crescent Moon at dusk forms a triangle with Jupiter to its left and dimmer Antares closer to the Moon's lower left, as shown at the top of this page.
• Algol is at its minimum brightness for a couple hours centered on 9:23 p.m. EDT.
Thursday, Oct. 3
• The thick crescent Moon this evening shines with bright Jupiter, as shown at the top of this page. Jupiter, though, is 2,200 times farther away. Its four big moons, visible in any telescope as 5th and 6th magnitude dots, are roughly our own Moon's size.
Friday, Oct. 4
• Now the waxing Moon shines between Jupiter and Saturn.
Saturday, Oct. 5
• It's both International Astronomy Day and International Observe the Moon Night! The Moon is first quarter (exactly so at 12:47 p.m. EDT), well placed high in the sky during early evening with its shadow-displaying terminator running right down the middle of the disk.
Moreover, this evening the Moon has Saturn as a companion — another top target for small scopes. As seen from North America, Saturn is only about 2° to the Moon's right or upper right. Perfect for setting up your scope in a public place and offering views of both as a sidewalk astronomer.
You can point out that Saturn is 3,800 times farther away. A telescope this evening will show its own largest satellite, Titan, as just a magnitude-8.7 orange pinpoint four ring-lengths to Saturn's east. Yet Titan is half again as large in diameter as our Moon.
Want to become a better astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.
This is an outdoor nature hobby. 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 guide to astronomy.
Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas (in either the original or Jumbo Edition), which shows stars to magnitude 7.6.
Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; nearly three times as many. The next up, once you know your way around, are the even larger Interstellarum atlas (stars to magnitude 9.5) and Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts with a telescope.
You'll also want a good deep-sky guidebook, such as Sue French's Deep-Sky Wonders collection (which includes its own charts), Sky Atlas 2000.0 Companion by Strong and Sinnott, or the bigger Night Sky Observer's Guide by Kepple and Sanner.
Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically (meaning heavy and expensive). And 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, Venus, and Mars remain deep in the glare of the Sun.
Jupiter (magnitude –2.0, between the feet of Ophiuchus) is the white dot low in the southwest as twilight fades away. Orange Antares, one sixteenth as bright at magnitude +1.0, twinkles 10° to Jupiter's lower right.
This is a lousy time for Jupiter telescopically. Not only is the low-altitude seeing a mess, but Jupiter has shrunk to just 36 arcseconds wide.
Saturn (magnitude +0.5, in Sagittarius) is the steady yellow "star" in the south during and after dusk. It's 26° upper left of Jupiter. Below Saturn is the handle of the Sagittarius Teapot. Barely above it is the dimmer, smaller bowl of the Sagittarius Teaspoon.
Uranus (magnitude 5.7, in Aries) is well up in the east by 10 p.m. daylight saving time. It's highest in the south around 2 a.m.
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) is Universal Time (UT, UTC, GMT, or Z time) minus 4 hours.
Audio sky tour. Out under the evening sky with your earbuds in place, listen to Kelly Beatty's monthly podcast tour of the heavens above. It's free.
"The dangers of not thinking clearly are much greater now than ever before. It's not that there's something new in our way of thinking, it's that credulous and confused thinking can be much more lethal in ways it was never before."
— Carl Sagan, 1996