Have you seen Venus yet this autumn? If not, then this evening is a great time to start.

Although Venus has been visible in the evening twilight for several months now, it's been pretty low by the time the sky gets dark. But the situation has been improving rapidly since the beginning of November. By mid-month, Venus is about 15° above the southwestern horizon a half hour after sunset for people at mid-northern latitudes, making it quite easy to see. And it's still above the horizon an hour after that, when the sky is fully dark.

But the evening of Monday, November 17th, is special for observers in the America. That's when Venus passes just a few arcminutes away from Lambda Sagittarii, also known as Kaus Borealis, the star at the top of the Sagittarius "Teapot." Venus is 600 times brighter than Lambda, so the star will be hidden in the planet's glare if you try to view it without optical aid. But any telescope, or even steadily supported binoculars, should show Lambda shining off Venus's edge. If you have a telescope, note also that Venus is distinctly off-round. It's now in its gibbous phase, 74% illuminated.

Next turn your telescope to Jupiter, 13° to Venus's upper left. You'll see that Callisto, the outermost moon, is just about the same distance from Jupiter as Lambda is from Venus. (Click here for our interactive Javascript applet showing the positions of Jupiter's moons.) And Jupiter outshines its moons by just about the same margin that Venus outshines Lambda. So just this one night, you get to see Venus as it would appear if it had a moon like one of Jupiter's.

Click here for more information on observing Venus.

Have you ever seen an asteroid? It's more fun — and much easier — than you might imagine. If you're new to the game, then Vesta, the brightest of the lot, is definitely the one to start with.

This is a great time to view Vesta, because the asteroid is directly opposite the Sun, and almost at its brightest and closest to Earth, on October 29, 2008. It remains quite bright through mid-November, then fades gradually toward the end of the year. But even on December 31st, Vesta will still shine brighter than any other asteroid ever gets throughout 2008.

Vesta is near the head of Cetus, which rises an hour or two after sunset in late October. You will get your best views when the asteroid is high in the sky, which won't happen for another couple of hours after that. But by late November, Vesta will already be quite high by the time the sky is fully dark.

In 2007, Vesta got just about as bright as it ever can, reaching magnitude 5.4. At that point, I could spot it easily from a dark location with just my unaided eyes. It will be much tougher to see naked-eye this year at its peak magnitude of 6.4. But it's a snap to find with binoculars. Just click here to download a printable chart in PDF format. Then locate the head of Cetus and start comparing what you see through the binoculars with what's printed on the chart. When you find a medium-faint "star" that isn't plotted on the chart but is on Vesta's track — you've found the asteroid! The chart shows stars to magnitude 7.5, Vesta's brightness in the last week of December.

What's so fun about viewing something that looks just like any normal 6th-magnitude star? To find that out, make a little sketch of how Vesta fits into the surrounding star field. Then come back a night or two later, look again, and you'll see that the asteroid has moved. Vesta is moving about ¼° per day, so its motion is quite obvious over a course of a few nights.

Through a telescope at medium to high magnification, Vesta's motion is obvious over much shorter time spans. The asteroid covers 0.6 arcminutes per hour, which is a substantial distance at 100×. Try it; I bet you'll like it!

For generations, amateur astronomers have measured the quality of their skies by the naked-eye limiting magnitude (NELM) — the faintest star that can be seen without optical aid. The relentless spread of light pollution has added a new urgency to this time-honored method. It's now possible to measure skyglow directly both from the ground and outer space, but NELM remains the only good way to compare current conditions against the past, to see how light pollution progresses over time.

Besides, only dedicated stargazers are likely to invest in a specialized device to measure skyglow, like Unihedron's Sky Quality Meter. But with a little help, every man, woman, and child with normal vision can estimate the limiting magnitude. And the Internet makes it possible to gather and correlate the data on a scale that was never possible before.

That's the idea behind the Great World Wide Star Count. Inspired largely by Fred Schaaf's article "Count Light Pollution Out" in the April 2007 Sky & Telescope, the 2007 World Wide Star Count collected 6,600 observations from participants on all seven continents — yes, even Antarctica.

This year's count runs during the two weeks of moonless evenings from October 20th to November 3rd. See the home page for details about how you can participate.

So why not pitch in? It will take just five or ten minutes of your time, and it's lots of fun. It's also a great opportunity to get your family and neighbors to look up at the sky. There's nothing like asking people to look for stars to make it painfully clear just how onerous poorly designed lighting can be.

On Friday night, September 19–20, observers in northeastern North America, eastern Canada, and western Europe have a fine chance to watch the Moon cover up stars in the Pleiades.

For North Americans, the action comes on the evening of the 19th with the Moon low in the east-northeast. For Europe the occultations take place high in the sky before or during dawn on the 20th. The Moon will be waning gibbous (73% illuminated). This means that stars will disappear behind its bright limb, where you’ll need a telescope to watch them go, and will reappear from behind the Moon’s dark limb, where binoculars might suffice.

For instance: seen from the New York City area, Maia disappears around 9:38 p.m. EDT, Taygeta 9:43, Alcyone 10:16. Electra reappears around 9:59 p.m. EDT, Taygeta 10:00, Celaeno 10:01, Maia 10:23, Alcyone 10:36.
For predictions at many other locations, check lunar-occultations.com/iota/pleiades08/pleiades.htm.

In classical mythology, Venus, goddess of love, was married to Vulcan, the ugly smith-god, but she had an enduring love affair with Mars, the god of war. This is, perhaps, a metaphor for how human passions cause unrest and strife. It's no accident that Homer, greatest of the Greek poets, depicted Aphrodite and Ares (the Greek names for Venus and Ares) as vain, cowardly, and self-centered.

Be that as it may, the planets Venus and Mars are perennial favorites. And now they're paired close together above the west-southwestern horizon shortly after sunset. From September 9th to the 15th, the two planets will be less than 1½° apart, visible together in a telescope at 30× or less. And at their closest, on September 11th, they'll fit together easily even at high power.

Venus, at magnitude -3.8, currently outshines Mars (magnitude 1.7) by a factor of 150. So while Venus is visible to the unaided eye as soon as the Sun sets, you will probably need binoculars or a telescope to see Mars. And while you're there, don't forget to look for Mercury. Although it's lower in the sky than Mars, it's also much brighter (magnitude -0.9 to -0.7), making it much easier to see.

The best time to start looking for these planets is right after sunset. That will give you plenty of time to locate Venus and find the other two planets before they get too low for good telescopic views. To see the changing positions of the planets, view our 1-megabyte Quicktime movie. You can stop it at any frame and go backward or forward to the specific evening you're interested in.

Venus is getting ever higher and easier to view. See Sean Walker's article if you want to view or image this planet in detail. But Mars is sinking rapidly into the twilight glow, getting increasingly difficult both to locate and to view. This conjunction with Venus is your last good chance until Mars reappears from behind the Sun in April 2009.

I went out to view Venus, Mars, and Mercury last evening, September 8th. Venus was the only planet I could see without optical aid, but the other two showed up nicely in binoculars and my 70-mm refractor once I'd mentally adjusted for the huge discrepancy in brightness. All three planets showed tiny but gratifying disks at 60×. Although Venus's disk was biggest by far, it was also the hardest to view because of its overwhelming brightness.

Please post your own observations as comments to this blog.

For more than a year, planetary observers in the Northern Hemisphere have been treated to a steady parade of our solar-system siblings particularly well placed at high declination.

That series has unfortunately come to an end with Saturn and Mars both receding into the evening twilight. Jupiter now commands the evening, but for most people in the U.S., Canada, and Europe, it's just too low in the sky to produce satisfying views.

Fortunately, Venus has just passed superior conjunction, and is already shining low in the western horizon shortly after sunset. While mid-northern observers will find Venus very low in the evening twilight, there's still plenty of fun to be had pursuing the brightest planet in our skies.

One easy project anyone can do is to see how early in the evening you can spot Venus. I've managed to see it roughly a half-hour before sunset with only my unaided eyes by placing myself in the shadow of a tree or building, then searching just to the west of the Sun about two hand-widths away, roughly at the 10-o'clock position from the Sun. Venus is so bright that it shines through daylight skies easily, but you have to know exactly where to look to find it. For help, check out our interactive sky chart to help narrow down the area of your search. Clear, transparent skies makes this much easier to do.

If you're still having troubler finding it, don't worry. Once a month the Moon glides by the area, giving you a visual cue to both focus your eye on and skip over to Venus much easier than on other days. The Moon will be about 6° southwest of Venus on September 1st.

Venus makes some beautiful pairings with other interesting objects throughout this apparition. On the evening of September 11, it passes roughly 20 arcminutes north of Mars. Eight days later, Venus passes just 2½° north of Spica.

Careful telescopic observing can reveal hints of the faint cloud bands that circulate around the planet roughly every four days. I've been able to detect these visually only a few times in the past, usually on days of excellent transparency and good seeing conditions. Observing through colored filters will enhance these features, and also dim the view enough to make these observations possible.

If you're into planetary imaging, these cloud bands can be recorded with monochrome cameras equipped with colored filters, and are easier to detect at shorter wavelengths. Due to a still poorly understood phenomena, the highest contrast features in Venuses cloud tops appear in the near-ultraviolet wavelengths around 365 nanometers. Special filters, such as the "U" filter in a UBVRI photometric filter set, will aid greatly in recording these ever-changing features.

Like all the other planets, your best photographic results will come when Venus is high in the sky, so I try to image it during daylight hours. Be extremely careful if you do this, as one glimpse of the Sun through a telescope or even a finderscope can cause permanent blindness.

Give any of these projects a try. You may just find yourself drawn back to our sister planet much more often than you expected to be.

Look eastward after darkness falls, and you'll see a gleaming beacon that outshines everything else in its vicinity. That's Jupiter! On July 9th, the king of planets reached opposition, the point in the sky opposite the Sun — it rose as the Sun set. Each night afterward it's been inching a little higher in the evening sky as darkness falls.

No matter how you look at it, Jupiter is so bright and easy to spot that it makes an inviting telescopic target. What makes Jupiter such a treat is that it offers more to see in a telescope than does any other planet. It's the only one that shows distinct features in almost any telescope. And it's got four large moons that hover nearby like bright fireflies.

Before tracking down Jupiter with your telescope, grab your binoculars and find a tree or wall to brace against while pointing them toward Jupiter. If your binoculars magnify at least seven times (they'll be marked "7×35" or "7×50," for example), you'll see Jupiter as a tiny white disk. Look closely to either side for a line of tiny stars. Each of those tiny blips is a Jovian satellite at least as big as our own Moon; they only look tiny and faint because they're more than 1,500 times farther away.

Put a low-power eyepiece (the one with the highest number engraved on its barrel) in your telescope, then maneuver the tube so that Jupiter is centered in the eyepiece.

You might see two, three, or four moons, depending on when you look. The count often changes from night to night (or, if you're patient, even from hour to hour). That's because while orbiting Jupiter they sometimes glide in front of the planet, behind it, or into its shadow. These hide-and-seek movements confounded Galileo Galilei when he first spied these "stars" in 1610. But he soon realized they were actually circling around Jupiter, forming a miniature solar system of sorts.

The moons are named Io, Europa, Ganymede, and Callisto — or, collectively, the Galilean satellites — and it's difficult to tell which one is which. Callisto is usually (but not always) farthest from Jupiter, and Ganymede is a little brighter than its siblings. Fortunately, help is just a few mouse clicks away, using our online guide to identifying them.

Now turn your attention to Jupiter itself, and two things should be noticeable. First, the disk may not look perfectly round. Jupiter is a "gas giant" — it consists almost entirely of hydrogen and helium, and the "surface" you see is actually the top of a thick cloud layer floating high in an atmosphere thousands of miles deep. Jupiter spins so rapidly, rotating completely in less than 10 hours, that its equatorial midsection bulges out a bit.

Second, you should be able to see that the planet has two tawny-colored stripes running parallel to the row of moons. These darkish cloud bands in the Jovian atmosphere are called belts, and the brighter ones are zones. The North and South Equatorial Belts straddle the bright Equatorial Zone like a cream-filled cookie sandwich. If your telescope's main mirror (or lens) is at least 6 inches, you might be able to pick out a few other belts and zones closer to Jupiter's poles.

The most famous cloud feature on Jupiter is the Great Red Spot, an enormous oval-shaped storm about twice the size of Earth. Astronomers have known about the Red Spot for at least 150 years, but there's still no agreement as to which chemical compounds create its distinctive color.

Be forewarned that seeing the Great Red Spot is a challenge to spot in a small telescope. Your best prospects will be when the spot is nearest the middle of Jupiter's disk, which is a snap to figure out thanks to our handy Javascript utility. The planet's rapid rotation means that these "windows of opportunity" last only about an hour, so be prepared to look for it over several consecutive nights. Also, don't expect to see a bright red blob. The spot's color is subtle — much closer to pale orange than crimson.

If I've whetted your appetite and you want to really delve into what Jupiter's disk has to offer, check out John McAnally's excellent guide to observing the planet.

Jupiter’s cloudtop “surface” is a lively place that has kept telescopic observers busy for centuries. The planet’s dark belts and light-hued zones change their appearance and sprout new features frequently. In the past, keen-eyed Jupiter observers eyeballed the comings and goings of new features, but these days much of the monitoring is done with high-quality CCD images obtained by amateur astronomers.

One newly discovered feature is the little red spot (LRS), which was first identified by John Rogers, British Astronomical Association’s Jupiter Section director. As Rogers recounts, “This spot appeared last winter while Jupiter was hidden behind the Sun. I noticed it on March 1st in images taken by amateur astronomers Tomio Akutsu in the Philippines and Anthony Wesley in Australia. Such spots in the South Tropical Zone (STrZ) are very rare.”

Since LRS’s discovery, the currents of the STrZ have carried it inexorably toward the Great Red Spot. Jupiter watchers wondered what would happen to the small spot when it encountered the GRS and the adjacent Oval BA (Red Spot Junior). The moment of fate arrived on July 3rd, when the LRS tried to squeeze through the narrow gap between the GRS and adjacent Oval BA like dough through the rollers of a pasta machine.

As of this date, the little spot’s ultimate fate remains unclear. The July 5th image by Japanese amateur Isao Miyazaki (seen here) and those by Wesley and others offer tantalizing hints that some material from the spot may have survived, perhaps destined to re-form on the other side of the GRS. One thing is certain — the nights ahead will be interesting ones for Jupiter observers!

Atmospheric features like the LRS provide scientists with valuable clues about the dynamics and composition of the Jovian atmosphere. Camille Carlisle’s May 28th report neatly summarizes some of the scientific interpretations.

Currently Jupiter is situated in eastern Sagittarius and visible all night long. The giant planet reaches opposition on July 9th. Under steady viewing conditions, a 4- to 6-inch telescope will show Jupiter’s Great Red Spot quite well, though larger instruments will likely be needed to detect whatever might remain of the LRS. Look on the following edge of the GRS, which is currently near Jovian System II longitude 121°. (Transit times for the GRS are given in the July issue of Sky & Telescope, page 66, and also here.)

A week after perihelion, Comet C/2007 W1 Boattini should now be visible in the dawn sky by observers in the Northern Hemisphere. Preliminary results on Seiichi Yoshida's website indicate that it's now roughly magnitude 5.5 — still near its peak brightness.

On July 4th, Comet Boattini is just 6° above the eastern horizon 90 minutes before sunrise at latitude 40° north. That's too low for easy viewing, and the sky is already beginning to get bright even then. But the comet appears roughly 2° higher on each succeeding morning, and the Moon doesn't start to interfere until July 16th. Meanwhile, the comet is likely to fade as shown on Yoshida's website, becoming a faint telescopic target by August.

So early July is the best time for northerners to see this comet — assuming that your're fanatical enough to get up at 3 or 4 a.m. Few people are likely to see the comet without optical aid, but it should be pretty easy to spot through binoculars as long as your light pollution isn't too bad. Click here to download a detailed chart. We eagerly await our first post-perihelion reader reports.

If you can find a spot with a completely unobstructed western horizon, you can watch an extraordinary sky show in August and September 2008. Every evening just after sunset, four planets and two first-magnitude stars combine to form fascinating and ever-changing patterns.

If you live in the Southern Hemisphere, you can watch the whole show with your unaided eyes, but you will need binoculars to appreciate it properly from mid-northern latitudes. Go outside ten minutes after sunset and scan the western horizon until you find brilliant Venus, shining at magnitude -3.8. Then look for the fainter planets.

Mercury (magnitude -0.5 to 0.5) joins Venus from mid-August through mid-September. Saturn (magnitude 0.8) is low at the beginning of August and disappears a couple of weeks later. Mars, the faintest by far at magnitude 1.7, starts August high to the left of Venus and ends September to Venus's lower right. Look also for Regulus and Spica, which are brighter than Mars but fainter than Saturn. And for the first three evenings of each month, a thin crescent Moon joins the show.

Click here to view a one-megabyte movie of the four-planet dance. After watching the general progression, step forward and back to see the configuration on any particular evening. You may need to install QuickTime to watch the film if you haven't already done so.

(Last updated June 6th.)

Serious comet chasers — people who track faint comets with telescopes and binoculars — have been aware of Comet C/2007 W1 (Boattini) for quite a while. It was forecast to become quite bright for a telescopic comet, 6th or perhaps even 5th magnitude, making it visible without optical aid to skilled observers at dark sites.

For a while, Boattini exceeded its brightness predictions by more than a magnitude. Now it has settled back to its predicted behavior. If it bumps up again — and that's a very big if! — it could become fairly prominent low in the east before dawn in July.

Right now (June 6th) the comet is deep in the southern sky and nearing the Sun, so it's visible only from the Southern Hemisphere. There, people have been seeing it without optical aid under ideal conditions. In late May Boattini was also spotted by many binocular observers in the southern tier of the United States.

As of early June the comet is crossing southern Canis Major. If you're at the latitudes of Australia and New Zealand, start looking for it in late twilight, and continue until the Sun's afterglow has completely disappeared. Click here for a detailed, full-page, printable chart showing the comet's path south of Sirius.

The comet passes directly south of the Sun in mid-June, making it invisible to anybody north of Antarctica.

Boattini will emerge from the Sun's glow around the beginning of July as an early-morning object, low in the east, for observers in both the Northern and Southern Hemispheres. What it will look like then is anybody's guess. Most likely, it will be a pleasant though unspectacular little binocular target. There's a small but significant chance that it will become brighter than any comet since Holmes's spectacular outburst late last year.

And there's an even smaller chance that the comet will disintegrate entirely while it's hidden in the Sun's glow and never be seen again. It wouldn't be the first time that's happened to a comet.

Here's a light curve and chart of its future path. Stay tuned to SkyandTelescope.com, and we'll keep you posted on the developments.

Mars is one of the half dozen swiftest-moving objects in the sky — not counting the occasional near-Earth asteroid or comet. Except when it’s closest to Earth, Mars moves through the stars at roughly 1.4′ per hour, or ½° per day. So it’s possible — though challenging — to track the planet’s progress from one night to the next with your unaided eyes.

But if you want to see Mars move during a single observing session, you’ll need a telescope, or at the very least binoculars.

A planet’s motion is easiest to see when there’s a bright star very nearby to provide a frame of reference. Stargazers in far-western Europe and Africa and the easternmost sections of the Americas had such an opportunity on the night of May 19–20, when Mars passed just north of the 5.3-magnitude Eta Cancri. The planet was less than 3′ from the star from 8:00 to 9:30 p.m. EDT on May 19th (0:00 to 1:30 May 20th Universal Time).

Circumstances are even better three nights later, when Mars plunges into Messier 44, the Beehive — a whole cluster of stars! A particularly close encounter is viewable low in the sky from America’s West Coast around 11:30 p.m. PDT on May 22nd, with Mars less than 1′ south of 6.4-magnitude 39 Cancri. A half hour later, the planet is directly between this star and its nearby 6.6-magnitude companion. Click here for a full-page, printable chart showing Mars's track through the Beehive.

Western Europe and Africa and the easternmost Americas are again favored for the closest approach of all, at 9:00 p.m. EDT on May 23rd (1:00 UT May 24th). That’s when you’ll find the planet’s center about 16″ — just 3 Mars diameters — north of a 6.9-magnitude star. If you look carefully, you should be able to track the planet’s motion almost continuously as it traverses 1.4″ every minute — moving its own diameter every 3½ minutes.

But wherever you’re viewing from, even if you miss these spectacularly close conjunctions, Mars’s passage through the Beehive will be an event you’ll never forget.

Did you get to see the crescent Moon occult the Pleiades last Tuesday night? Conditions here in Boston were pretty iffy, but things worked out alright in the end.

Both the National Weather Service and the Clear Sky Chart had good forecasts, so I felt confident scheduling a little observing party in our local park with my family and a couple of friends. But thick clouds began to cover the sky at sunset, and prospects were looking grim. Fortunately, the clouds thinned out, leaving just a medium-heavy haze by the time the Moon neared the Pleiades.

Because of the haze, the cluster was completely invisible to the unaided eye, and I could see only the brightest stars through my 10×30 binoculars. But my 15×70 binoculars, 70-mm refractor, and 7-inch Dob all had enough power to show dozens of stars, so three people got to watch each occultation simultaneously. Every disappearance was greeted with little cries of delight. Overall, the 15×70 binoculars probably provided the most aesthetically satisfactory view.

Saturn and Mizar provided icing on the cake, particularly for one friend who had never seen Saturn before. Which all goes to show that even haze and heavy light pollution don't have to stop you from having a great observing experience.

If you have any stories of your own, please submit them as comments below.

The first time I knowingly saw the zodiacal light, it was so bright that I couldn't believe I'd never seen it before. I was in Chile, across the valley from the professional observatories at Cerro Pachon and Cerro Tololo. I commented to my host, the superb astrophotographer Daniel Verschatse, that the light pollution from nearby La Serena was unbelievably intense. The light in the west was washing out even the Sagittarius Milky Way, which was quite high in the sky at the time.

"Look again," said Verschatse. "That's not light pollution; it's the zodiacal light! See its tall, triangular shape? See how it leans to the right, following the ecliptic?" (In the north, the evening zodiacal light leans left, as shown at right.)

Now that I know what to look for, I see the zodiacal light quite often. I've even seen it — just barely — from my astronomy club's observing field in the outer Boston suburbs. But it's much more prominent if you're far from any artificial light pollution. It's well worth the trip.

The zodiacal light is brightest and broadest near the Sun. But the very brightest part of all can never be seen from Earth, because it's overwhelmed by the Sun's glare. So your best opportunities come right before the onset of morning twilight and after the end of evening twilight, when you can see the sky quite close to the Sun, but the Sun's light is blocked by our own planet.

And since the zodiacal light follows the ecliptic, it's easiest to see when the ecliptic runs highest in the sky near twilight, as shown at right. In the Northern Hemisphere, that happens during the evening from mid-February through mid-April, and in the morning from mid-August through mid-October. (The situation is reversed in the Southern Hemisphere, which is why I could see the zodiacal light so easily on an October evening in Chile.)

Most people prefer to view in the evening, so late winter and early spring are the ideal time. Find spot as far as possible from any artificial lights that has a low western horizon. Go there shortly after sunset on a moonless evening and watch for the zodiacal light to appear as twilight fades.

What are you seeing? The zodiacal light is the combined glow of countless tiny particles (debris from comets and asteroid collisions) that orbit the Sun. Like the dust in an unswept room, their mass is minuscule but their combined surface area is quite large, so they reflect a lot of sunlight. In fact, if it could be condensed into a single point, the zodiacal light would handily outshine all the planets, including even Venus.

As an interesting side note, Brian May, founding member of the rock group Queen, completed his doctoral dissertation on the zodiacal light in 2007, obtaining a PhD in astrophysics from Imperial College in London. He had started the thesis in 1970, but took a 35-year break to become a rock celebrity.

Have you seen the zodiacal light? Then share your impressions below with the rest of our readers.

Did you know that Venus is still visible in the morning sky? I have it on the best authority. There's a chart showing planet visibility in the middle of every issue of Sky & Telescope, and the one on page 47 of the April issue says that Venus is visible just before dawn through April 12th.

But wait a second! Things can't be as simple as that. Venus barely changes from day to day, so it can't just sit there in plain view on the 12th and disappear completely on the 13th. The transition must be subtle.

Moreover, any planet's visibility depends on your latitude, the clarity of the air, your level of experience, and the equipment that you use. Just what does this chart mean when it says Venus is visible?

As author of the chart, I can answer those questions. First of all, we're talking about visibility to the unaided eye. With a telescope, you can see all the bright planets just about any time they're above the horizon when the sky is clear — even during broad daylight.

And unless otherwise stated, all articles and diagrams in our magazine are intended to be precisely accurate for the "S&T standard location: 40° N, 90° W, 55 miles southwest of the proverbial Peoria, Illinois.

Finally, I know perfectly well that visibility isn't an either/or situation, but I have to put down some date. I have a formula based on a planet's brightness and its altitude above the horizon at the beginning or end of civil twilight that predicts when it should be visible to an experienced observer with good-to-excellent conditions. And I'm constantly tweaking this formula based on my own and other people's observations.

That's where you come in. My formula predicts that Venus should be visible very low in the east 15-20 minutes before sunrise through mid-April. Please go out, look for yourself, and report any positive or negative sightings to us. The key to a successful observation is finding a location with a completely unobstructed eastern horizon. And binoculars are extremely helpful, because Venus is bright and bold in binoculars even when it's barely visible to the unaided eye.

The morning of Friday, April 4, is a particularly good oppoprtunity, because Venus will be right next to a thin crescent Moon.

Please submit any reports as comments to this article or e-mail them to observers@SkyandTelescope.com. Include your location, the sky conditions, and the time accurate to one minute.

For instance, I went to my local park (42.1° N, 71.1° W) on the morning of Wednesday, April 2nd. The sky was clear though slightly hazy, with a few wispy clouds to the east. I found Venus in binoculars at 6:03, and it was consistently visible to the unaided eye from 6:05-6:10 — though pretty faint and subtle. I caught my last naked-eye glimpse at 6:20, just before I left, but by that time I was seeing it less than 5% of the time. It was still bright and bold in binoculars, and no doubt would have stayed that way until sunrise.

Incidentally, I was also following Jupiter, far off to the south. It was still quite obvious to the unaided eye at 6:20 — as long as I looked in exactly the right spot. I lost track of Jupiter once and spent several minutes searching for it with binoculars.

And two last questions — which you're also welcome to answer in e-mail or (better) as a comment to this article. Our planet-visibility chart is intentionally optimistic; it says when planets are likely to be visible — even if just for a few minutes — given ideal circumstances. Does this lead to unrealistic expectations? Would you prefer to know only when the planets are likely to be easy to see?

Finally, do you like the format of the planet-visibility chart? Does it tell you everything that you need to know? How would you like to see it changed, if at all?