The Old Farmer's Almanac 2015 (9 page)

The Moon’s Path

The Moon’s path across the sky changes with the seasons. Full Moons are very high in the sky (at midnight) between November and February and very low in the sky between May and July.

Next Total Eclipse of the Sun

March 9, 2016: visible from Indonesia and the North Pacific Ocean.

Transit Times

This table shows the time (EST or EDT) and altitude of a star as it transits the meridian (i.e., reaches its highest elevation while passing over the horizon’s south point) at Boston on the dates shown. The transit time on any other date differs from that of the nearest date listed by approximately 4 minutes per day. To find the time of a star’s transit for your location, convert its time at Boston using Key letter C (see
Time Corrections
[>]
).

Rise sand Set Times

To find the time of a star’s rising at Boston on any date, subtract the interval shown at right from the star’s transit time on that date; add the interval to find the stair’s setting time. To find the rising and setting times for your city?, convert the Boston transit times above using the Key letter shown at right before applying the interval (see
Time Corrections
[>]
). The directions in which the stars rise and set, shown for Boston, are generally useful throughout the United States. Deneb, Algol, Capella, and Vega are circumpolar stars—they never set but appear to circle the celestial north pole.

Twilight is the time when the sky is partially illuminated preceding sunrise and again following sunset. The ranges of twilight are defined according to the Sun’s position below the horizon. Civil twilight occurs when the Sun’s center is between the horizon and 6 degrees below the horizon (visually, the horizon is clearly defined). Nautical twilight occurs when the center is between 6 and 12 degrees below the horizon (the horizon is distinct). Astronomical twilight occurs when the center is between 12 and 18 degrees below the horizon (sky illumination is imperceptible). When the center is at 18 degrees (dawn or dark) or below, there is no illumination.

To determine the length of twilight: The length of twilight changes with latitude and the time of year. Use the
Time Corrections
[>]
table to find the latitude of your city or the city nearest you. Use that figure in the chart above with the appropriate date to calculate the length of twilight in your area.

To determine when dawn or dark will occur: Calculate the sunrise/sunset times for your locality using the instructions in
How to Use This Almanac
[>]
.
Subtract this length of twilight from the time of sunrise to determine when dawn I)reaks. Add the length of twilight to the time of sunset to determine when diarie descends.

Listed here for Boston are viewing suggestions for and the rise and set times (EST/EDT) of Venus, Mars, Jupiter, and Saturn on specific days each month, as well as when it is best to view Mercury. Approximate rise and set times for other days can be found by interpolation. Use the Key letters at the right of each listing to convert the times for other localities (see
Left-Hand Calendar Pages
[>]
and
Time Corrections
[>]
). For all planet rise and set times by zip code, visit Almanac. com/Astronomy.

Venus

Venus’s apparition cycle repeats every 8 years. This year offers a reprise of its wonderful 2007 appearance. Venus is bright and obvious as soon as the year begins, a brilliant evening star low in the west after sunset. It stands higher and brighter at dusk through the winter and reaches its highest point in April and May, when it sets 3½ hours after sunset. Lower but even brighter in June, Venus vanishes behind the Sun in a conjunction on August 15 before quickly reappearing as a morning star in the predawn east in late August and standing spectacularly high and dazzling in September. Venus slowly fades for the rest of the year.

Mars

Mars becomes brilliant and ventures close to Earth every other year. This is a Martian “off’ year. The planet starts the year dim and low in the west at dusk and meets blue Neptune telescopically on January 18 and 19, and then the crescent Mooil on January 22. Faint in the southwest at nightfall, Mars closely meets Venus from February 19 to 21. The crescent Moon spectacularly join’s this tight but low conjunction on February 20. Mars vanishes in the Sun’s glare in March. It reappears in August in Cancer, low and faint, and finishes the year near Virgo’s blue star Spica, rising at around 2:00
A.M.

Jupiter

The largest planet begins the year conspicuously in Leo, rising after nightfall. Retrograding into Cancer in February, Jupiter has its opposition on the 6th, when it is out all night. Jupiter remains an evening star through June, when it returns to Leo and spectacularly stands near Venus and the Moon on the 19th and 20th. June 29 starts a beautifully tight 5-day meeting with Venus, low in the west at dusk. It remains visible for July 4 revelers but sinks into the solar glare by month’s end. Jupiter strikingly reappears in October as a morning star in the predawn east. By year’s end, it rises before midnight.

Saturn

Saturn begins 2015 in Libra, rising just before dawn. This year, its famous ice rings are nearly fully “open,” making the planet brighter than it has appeared in more than a decade. In mid-March, in Scorpius, Saturn starts rising at around midnight. It rises before 11:00 P.M. in mid-April and at nightfall in mid-May. At op position on May 22, Saturn is out all night and remains a bright evening star through August. Gorgeous through backyard telescopes, Saturn starts sinking lower in the southwest at nightfall in early autumn. It becomes too low to observe by mid-October and hovers behind the Sun in a conjunction on November 29.