Northern Hemisphere gazer's guide
Oct. 4: If you have been watching Venus in the morning sky (rising about 3 a.m. daylight time), you may have seen it pulling closer to the bright star to its left (east), Regulus, in Leo. Later today, Venus passes the star, and beginning tomorrow morning you will see it separating to the left from Regulus. The crescent moon is nearby (to the right) on the morning of the 4th also. When you look tomorrow morning, it will be to their left and closer.
Oct. 5: This morning's sky is more attractive, if anything, than yesterday's. Venus, Regulus, and the waning crescent moon are even closer. You can see them from moonrise until they fade in the brightening dawn.
Oct. 9: The moon is at apogee, the position in its orbit where it is most distant from earth.
Oct. 10: Mercury is at its greatest distance to the sun's left (greatest easterly elongation), the position that locates it most favorably as an evening star. During this cycle of its configurations, however, Mercury is not well placed for viewing.
Oct. 12: Mars is not very well placed as an evening star and not very bright. But you may be able to see it tonight by using the waxing crescent moon as a guide. Mars is located well below the moon until about two hours past sundown, when it sets. Don't confuse it for Antares, the reddish star in Scorpius, a bit brighter than Mars and lower.
Oct. 20-21: Tonight is best for hunting the Orionid meteors. Begin looking about 1 a.m. on the 21st, when the earth has turned us to face in the direction of the incoming particles. Select a location and position yourself to scan as much of the sky as possible. After you have seen one or two so-called "shooting stars," your experience will help you build up to the 25-per-hour rate we expect from this moderately productive shower. Its meteors are swift, and can be quite bright. You might see up to 15 meteors per hour on the morning before and after.
Oct 23: Mercury is moving swiftly past earth now, on its way toward inferior conjunction (when it passes between earth and sun). This causes it to become stationary (relative to the stars in its direction) today and to move westerly (retrograde) relative to them during the next three weeks.
Oct. 22-24: The full moon of Oct. 23 is known as the hunter's moon. Because of the low inclination of the moon's orbit to the eastern horizon at sundown at this time of year, the retardation (delay in the time of moonrise) on the successive nights of the 22nd, 23rd, and 24th makes it seem as though the full (or nearly full) moon remains with us for three nights in a row, filling the early evening sky with bright moonlight on each night.
Oct. 23: The moon is at perigee (nearest earth) only nine hours before it is full. The effect of perigee will enhance the normally stronger spring tides that occur twice monthly (when the moon is full or new, and earth, moon, and sun are in line). Look for exceptionally strong high tides (and low) today, tonight , and tomorrow afternoon.
Oct. 24: Mars is in conjunction with Antares (the star in Scorpius) today, passing closest to it from west to east. But the two objects set too soon after sundown to be seen.
Oct. 25-26: The star near the moon from moonrise (about 8 p.m. daylight time) on tonight is Aldebaran, in Taurus. Watch the moon approach the star throughout the night, until it passes Aldebaran about 6 a.m. EST on the 26th. The moon covers the star (an occultation) over northern Canada and Alaska.
Oct. 26: Communities on daylight time set clocks back one hour early today to convert to standard time.
Oct. 30-31: Look for Jupiter and Venus in the eastern sky on both mornings, from about two hours before dawn until just before sunrise. Venus is the brighter of the two, but Jupiter is no slouch! They will be very close to one another on both mornings, a bit closer on the 30th. But from Thursday until Friday morning they will change places. Venus will pass above Jupiter from right to left and then move away to the left (east) on successive mornings.
All Month: During October, Jupiter joins Venus in becoming prominent in the morning sky. Venus is not quite so impressive as it has been, not as bright, rising a bit later, and not so high at dawn. Jupiter, on the other hand, is steadily improving, rising earlier and appearing higher at dawn. You may need the the moon to guide you to Jupiter on the 7th, but after midmonth the planet stands well enough above the horizon at daybreak to be seen easily. Jupiter will be lower than Venus all month; it will rise later than the brighter planet but the distance between them continually diminishes. Venus is moving east (to the left) much more rapidly, catching and passing Jupiter at the end of October. By then, Saturn comes into view in the morning, lower than Venus and Jupiter.
From Oct. 30 to Nov. 3, Venus is between Jupiter and Saturn, and for the last week of October and the first week of November the three bright planets will make an exceptional grouping in the dawn sky, joined by the waning crescent moon on the morning of Nov. 4.