SKY_September2014.pdf

50 September 2014 sky & telescope

OBSERVING

Celestial Calendar

Ice-Giant Spotting

Uranus and Neptune are in reach of binoculars as they go their separate ways.

AQUARIUS

PEGASUS

PISCES

α

χ

φ

γ

η

κ

λ

ο

π

ρ θ

σ

ψ^1

ψ^2

ζ

51

η

ι

θ

α

ε

γ

ν

θ

ξ

ζ

ε δ

γ

ι

λ κ

θ

ω

ζ

19

80 Path of Uranus

Path of Neptune

22 h 00 m

+10°

–10°

0 °

1 h 00 m 0 h 30 m 0 h 00 m 23 h 30 m 23 h 00 m 22 h 30 m

Star magnitudes

4

3

5

6

7

If you came into amateur astronomy later than 1975,

you’ve never known Uranus and Neptune to be as far

apart as they are now: 40°. For decades, it seemed like the

twin outer planets were naturally twinned on the sky as

well. And among those who were around at the time, who

can forget their pairing in 1993, when they fi t into the

same low-power view just 1.1° apart?

50 September 201 4 sky & telescope

Saturn’s Rhea to Occult a Star

An unusual event happens early on the evening of

September 12th for telescope users in North America.

Saturn’s second-largest satellite, 10.2-magnitude Rhea, will

occult a 7.8-magnitude star.

The occultation will be visible from much of the north-

eastern United States and Ontario. Observers south of there

will see a very near miss, and watchers in the west will fi nd

the star moving away from Rhea by the time darkness falls.

You’ll need a good view low to the southwest; Saturn and

its retinue will be sinking toward the horizon during and after twi-

light. Saturn is the right-hand point in a roughly horizontal row of

three, Mars is in the middle, and Antares is on the left.

The occultation happens around 8:38 p.m. Eastern Daylight

Time; 7:38 p.m. CDT. The farther east you are, the lower Saturn

will be. The farther west, the more likely the event will occur while

the sky is still too bright. By the time darkness arrives on the West

Coast, Rhea and the star (SAO 159034) will be well separated.

The second-brightest point in the immediate fi eld of view will

Those times aren’t coming back until the 22nd cen-

tury. Uranus, in its faster orbit, is pulling ever farther

eastward away from Neptune. Pretty soon we’ll have to

stop including them in the same annual wide-fi eld fi nder

chart like the one above.

The black rectangles show the areas of the deeper

close-up charts, with date ticks, on the facing page.

CC layout.indd 50 6/23/14 12:17 PM