Neptune, the Solar Systems most distant and faintest planet is only a few weeks away from opposition and now well placed for observation. At opposition on August 27th, the planet will be 28.973 AU (approx. 4334.3 million km or 2693.2 million miles) from Earth and at its brightest for the year. However, with a peak magnitude of +7.8 you won't be able to see the distant ice giant with the naked eye. However it's a relatively easy binoculars target, provided you know exactly where to look.
Locating Neptune
Throughout 2013, Neptune remains in the constellation of Aquarius. It starts the year moving direct before reaching its first stationary point on June 7th. It then starts retrograde motion, moving westwards against the "fixed" background stars. Neptune then passes through opposition before reaching its second stationary point on November 13th, after which it once again resumes direct easterly motion.
Aquarius is a faint zodiac constellation with its brightest stars being of only 3rd magnitude. Neptune is currently positioned almost exactly bang in the middle of the constellation, about 1 degree to the west of star Sigma Aquarii (σ Aqr) mag. +4.8. Located about 30 degrees NE of Neptune is the "Square of Pegasus" and about 20 degrees SE of Neptune is the brightest star in the surrounding region; Fomalhaut (α Psc) at magnitude +1.2.
Neptune Finder Chart for July 2013 - pdf format
With a current declination of -10 degrees, Neptune is better situated for observation from the tropics or southern hemisphere, where it appears higher in the sky, compared to northern latitudes. At the end of July, the planet rises shortly after sunset and remains visible for the remainder of the night.
Neptune July 2013 Data Table
| Date | Right Ascension | Declination | Apparent Magnitude | Apparent Size | Illumination (%) | Distance from Earth (AU) | Constellation |
|---|---|---|---|---|---|---|---|
| July 01, 2013 | 22h 28m 27.5s | -10d 17m 09.1s | 7.9 | 02.3" | 100 | 29.403 | Aquarius |
| July 06, 2013 | 22h 28m 12.4s | -10d 18m 46.2s | 7.9 | 02.3" | 100 | 29.335 | Aquarius |
| July 11, 2013 | 22h 27m 54.7s | -10d 20m 37.8s | 7.9 | 02.3" | 100 | 29.272 | Aquarius |
| July 16, 2013 | 22h 27m 34.6s | -10d 22m 42.7s | 7.8 | 02.3" | 100 | 29.214 | Aquarius |
| July 21, 2013 | 22h 27m 12.4s | -10d 24m 59.8s | 7.8 | 02.3" | 100 | 29.161 | Aquarius |
| July 26, 2013 | 22h 26m 48.2s | -10d 27m 27.8s | 7.8 | 02.3" | 100 | 29.114 | Aquarius |
| July 31, 2013 | 22h 26m 22.2s | -10d 30m 05.3s | 7.8 | 02.3" | 100 | 29.074 | Aquarius |