January 20, 2020

Astro-Event(s): Lunar/Planetary Action & Hunting Triton.

Mars, Saturn & Spica the night of MSL’s Landing. (Photo by Author).

We’re swiftly losing the evening planetary action this month, as Jupiter, Mercury and Venus occupy the dawn skies and Saturn and Mars slide ever lower into the dusk. It’s interesting to watch as Mars appears to “pass” the Spica & Saturn pairing in the constellation Virgo as its orbital motion struggles to keep up with Earth. Mars finally reaches conjunction with the Sun on April 17th, 2013 & as we mentioned earlier this month, the Red Planet is now home to our newest planetary embassary, Curiosity.

The Moon passes Spica as seen from North America the night of August 21st.

(Created by the author in Starry Night).

The trio of Mars, Saturn and Spica also gets a visit from the 4-day old crescent Moon on the evening of August 21st. The Moon will lie less than 2 degrees from Spica and should display Earthshine or Ashen light “betwixt the horns” of its 23% illuminated crescent. The Moon will actually occult Spica as seen from Antarctica at 22:00 UTC on August 21st, the 2nd of a series of 18 occultations of the +1 magnitude star occurring through 2012-2013. These occultations will creep slowly northward, and Europe will get its first good Spica occultation by the Moon on September 8th, 2013, with North America following on November 29th of the same year.

But all is not lost for evening planetary action this week. Neptune reaches opposition for 2012 on Friday, August 24th at 9:00 AM EDT/13:00 UTC, and now is a great time to try and spot the +7.8 magnitude planet as it slowly moves through the constellation Aquarius. In fact, the planet will be within a degree of the +5.4 magnitude star 38 Aquarii on the night of opposition, & approaches it within 20′ in early October, making it another great guide to the planet.  Neptune displays a tiny 2.3” wide grey-to-blue disk visually at moderate powers, looking like a very tiny planetary nebula that refuses to come to a pinpoint focus.

Finding Neptune… (Created in Starry Night).

Although the Moon reaches 1st Quarter on the 24th, the best time to hunt for Neptune will be at local midnite, when it’s transiting and highest overhead. Said 1st Quarter Moon will also be setting around that time, though it’ll become more of a light polluting factor as it heads towards its second Full Moon of the month on August 31st (more on that next week!)

But wait, there’s more… “Been there, done that” when it comes to nabbing the ice giant worlds? How ‘bout taking a stab at its largest moon, Triton? We wrote about this wacky world and how to track it down last year. Triton shines at magnitude +13.5, and opposition is the best time to tease it out with a moderate-to-large sized scope. Triton orbits Neptune once every 5.9 Earth days, and reaches a greatest elongation of 18” from the disk of Neptune twice an orbit, the best time to try and sight it. Opportunities for 2012 are below;
























Ephemeris chart created by Ed Kotapish.

Corkscrew chart for the elongations of Triton. (Credit: NASA/PDS Rings Node).

Neptune’s position the night of opposition is;

Right Ascension: 22Hours 15’ 54”

Declination: 11° 26’ 06”

Note that astro-imaging maestro Damien Peach grabbed the pair, complete with detail! Do try to hunt down this fascinating world, a possible twin of Pluto that has only been visited once by humanity, when Voyager 2 passed Triton in 1989. Will New Horizons reveal a similarity between the pair when it passes Pluto in 2015? We’re less than 3 years away from finding out!



  1. [...] 21st: Moon occults Spica as seen from the Antarctic, one of five Spica occultations by the Moon to occur in [...]

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