Above is a to scale location representition of Mercury at Sunset.  Each Dot represents 1 Day's Position.  The "W" is Due West on the Horizon.  Note that Mercury, for us, like the Moon and Venus, goes through Phases.

Mercury is "bright". At it's brightest, < Mag. 2.0.  Only the Sun, Moon, Venus, Mars (at it's brightest), and Jupiter are brighter.This Apparition, Mercury will reach Mag. + 0.6.  Not many living people have "seen" Mercury, perhaps only 100,000,000.  That's because, with an Interior Orbit to Earth, Mercury's maximum Elevation at Sunset, for us, above the Horizon, is 28 degrees and usually much lower.  Because it's low in the Twilite Glow, it's difficult to see less than 30 - 45 mins. after Sunset.  Additionally, Mercury is difficult to see if it's Angular Separation from the Sun is less than 12 degrees.

Mercury is a "small" Planet, about one-seventeenth the Volume and Mass of Earth.  It's the fastest Sun-Orbiting Planet - average speed is 30 mi./sec.  Earth's average speed is 18.5 mi./sec.  Mercury has the most Eccentric Orbit of the "Planets" at .21.  At Perihelion (closest to Sun) it's 29,000,000 mi.,  at Aphelion (furthest from Sun) it's 43,000,000 mi.  Mercury gets from 5 to 11 times the intensity of Sun Light as Earth.  Without an Atmosphere, it's even more intense on Mercury's Surface, with an average Surface Temperature of 629 degrees F.

With Earth's and Mercury's Orbits, its Synodic Period is about 116 Days.  Which means it has Eastern Elongations about 116 days, on average.  There's a Western Elongation, on average each 116 Days.  Since I don't like to get up early, I observe Eastern Elongations (when Mercury is visible in the Western Evening Sky after the Sunset).  The next Mercury Eastern Elongations will be Dec. 2010,  Mar. 2011, & July 2011.  I'll probably observe the July 2011 Elongation, maybe the others.

If you want to see Mercury, you'll need a Low Horizon - free of buildings, trees, hills or other obstructions.  At its highest this Apparition, Mercury will be less than 16 degrees above the Horizon at Sunset.  I plan to be at Mt. Pollux, Amhest, Sunday - July 18 & 26, & Friday - July 30, before 8 pm.  Then Friday - Aug. 6 & 20, and Sunday - Aug, 1, 8 15, & 22 by 7:30 pm.  If you want to see Mercury on those dates, please call me, Tom Whitney at  256-6234, between 5 & 6 pm on those dates, or email me at  tom-whitney@tom-whitney.com  , the day before.  I'll meet you and bring extra equipment to Mt. Pollux for this.  If you want to do other dates, notify me at least a day ahead and, if I can, I'll try to accommodate you.

Hope you can "see" Mercury this Apparition.  If so, you'll be in an exclusive group on only 100,000,000 +/- living people.  If you "see" the Cresent of Mercury, you'll be in an even more exclusive group of 10,000,000 +/-, living. 

-  Tom Whitney

Moon & Venus July Repeat

Above is a scale representation of what you will see looking West after Sunset. if Sky is Clear, on July 14, 15, & 16.  Moon noticably appears to move through the Sky Daily, while Venus only appears to move slightly against the background Sky.

July 14th to 16th, the Crescent Moon & Venus again put on a spectacular display in the Western Evening Sky, just after Sunset, similar to their June display.  Moon & Venus are consistantly the 1st & 2nd brightest natural Night Sky Celestial Objects.  Each are bright enough to be seen from an urban light polluted Sky.  They will show a somewhat similar, but not identical, display monthly through October.  The next similar apparition will be August 12 to 15.  However, Venus will be 5 degrees lower in the Sky, while slightly brighter & larger.  Binoculars will show exquite detail on the Moon & possibly the Gibbous Dist (apparent shape) of Venus, particularly if you have premium optics & excellent eyesight.  A small telescope will show the apparent Gibbous Shape of Venus.  Venus displays an Evening Phasing about every 19 months, lasting almost 10 months, similar to the Moon's Monthly Phasing, because Venus' Orbit is interior to Earth's Orbit around the Sun.  A Telescopic view of Venus at 50 power will easily show it's apparent Gibbous shape.

Venus is so bright, Magnitude -3.8 to -4.6, it casts a shadow in a dark location.  Venus never appears more than 47.8 degrees from the Sun, for us in Amherst.  Usually it's much closer.  So it's isn't seen by us in the Dark Midnight Sky.  For us, Venus is always seen in the lovely Twilight Glow after Sunset or before Sunrise.  Part of the reason ancient Greeks named it after the Goddes of Beauty.

If you want to see this spectavular July Apparition, look West at Sunset.  Don't look at the Sun !  Venus will be about 20 degrees above the Horizon.  You man need an unobstructed Horizon - free of trees, buildings, hills, or other obstructions.  Venus will Set about 2 hrs. after the Sun.

If you want to see this Apparition in a Telescope, call me - Tom Whitney at  256-6234  between 6 & 7 pm, July 14 or 15.  If Clear, I'll meet you at Mt. Pollux around 8 p.m., with a Telescope.  If Clear on Friday, July 16, I'll be at Mt. Pollux by 8 p.m., with my Astronomy Class.

The next Evening Appritions of Moon & Venus that will somewhat approximate these current ones, will be December to March 2011 - cold & unpleasant New England weather, with the Moon & Venus lower in the Sky.  The next Apparitions as "good" as this will be in 2018.  Hope you can see this, if your schedule & weather permit.

-  Tom  Whitney