Sky and Telescope - May 2012 - (Page 52)

OBSERVING

Celestial Calendar

After the new Moon is done occulting a big star (the Sun) on May 20th, it moves eastward along its orbit to become a thin waxing crescent that will occult a much more distant star, 3rdmagnitude Zeta Tauri, on the afternoon or evening of May 22nd. Zeta Tauri is the dimmer of the two horn tips of Taurus. This will be a tricky telescopic observation near the eastern edge of the visibility zone, where the star and Moon will be very low, and in the western part of the zone, where the star and Moon will be fairly high but the occultation will start either in bright twilight or broad daylight. The lunar crescent will be very thin, just 4% sunlit, and only about 23° east (upper left) of the Sun. If you’re trying to locate the Moon before sunset, set up your telescope just inside the shadow of a building, so there’s no chance of inadvertently viewing the Sun. Then scan carefully with your ﬁnderscope or binoculars
Ph
ns as er qu ke C D Cit La e ity en y Lo sV ve sA eg r as ng ele s

roughly 18° above and 12° to the left of the Sun. (This will vary with your location.) The star’s visibility in your scope will depend on sky conditions. It will disappear behind the Moon’s dark limb, as almost always happens for occultations when the Moon is waxing, but even with earthshine the dark limb may be invisible in a bright sky. So interpolate very carefully between the yellow lines on the map, or better, see the timetable of local predictions available at skypub.com/may2012lunaroccn. When you’re watching the star in the eyepiece, don’t blink at the critical time or you might miss it! The star reappears up to an hour or more later from behind the crescent’s bright limb. By then your sky will be darker but the Moon will be lower. Again, there will be no warning, so watch steadily as the critical time counts down. The two maps at right tell the story for each event.

2:1 0U T

Horn Tip Occulted

Disappearance
No rth er nl im it o fo ccu

2:2 0

Disappears in daytime

lta tio n

No occultation

2:3 0

Disappears in twilight

Disappears in a dark sky

2:5 0U T

Reappearance
Reappears in daytime

3:0 0
3:1 0

No rth

ern lim it o fo ccu lta tio n

3:20

nix

Moon Occults Zeta Tauri
May 22, 2012

Reappears in twilight
3:30 UT

No occultation

Reappears in a dark sky

Mark your location with a pencil dot, then interpolate between the yellow curves to ﬁnd the Universal Time of Zeta Tauri’s disappearance and reappearance. Remember that 0:00 Universal Time is 7:00 p.m. Central Daylight Time; 6:00 p.m. MDT; 5:00 p.m. PDT. Shading indicates whether the event occurs in daylight, twilight, or (for a tiny sliver of land) in darkness. The farther east you are in the occultation zone, the darker the sky but the lower the Moon will be.

S&T: LEAH TISCIONE (3)

52 May 2012 sky & telescope

Table of Contents for the Digital Edition of Sky and Telescope - May 2012

Sky and Telescope - May 2012
Table of Contents
Spectrum
Letters
75, 50 & 25 Years Ago
News Notes
Saturn’s Raging Superstorm
Stars Above, Earth Below: Astronomy in National Parks
The Remarkable Case of Comet Lovejoy
In This Section
May’s Sky at a Glance
Binocular Highlight
Planetary Almanac
Northern Hemisphere’s Sky
Sun, Moon, and Planets
Celestial Calendar
Exploring the Solar System
Deep-Sky Wonders
Going Deep
S&T Test Report
New Product Showcase
Telescope Workshop
Planetary Imaging with Your DSLR Camera
Gallery
Focal Point

Sky and Telescope - May 2012