Mercury at greatest elongation: morning sky

Event Date: August 16th
Time: 8:30 PM


Brief

   Mercury is well placed now in the east before Sunrise, at greatest western elongation.  Along with Venus, Jupiter and Sirius, which I showed yesterday slowly forming another triangle (to go with the Vega/Deneb/Altair shape in the west at this hour), I label Mercury below.  Lower to the horizon, is also a very old crescent Moon, which may be just barely visible before Sunrise, as a sliver.
The orbits for the planets also show with the ecliptic.
   The second image shows Mercury (mag 0.0) approaching dichotomy, zoomed in to about magnification 200x.  Currently, Mercury is at 42% illuminated, reaching the halfway point on the 18th. 

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

Mercury is only 18.7º separated from the Sun, as it is only about a week and a half from perihelion.  Therefore, as it loops back behind the Sun, viewed from us on Earth, it will be a little closer than average to us.  Therefore, as it continues to wax, the apparent magnitude of Mercury will quickly increase.  For the next week, with the geometry of the morning eastern sky still improving, Mercury spends the next couple of days rising 90 minutes before the Sun.  This is not the greatest rise-gap that we see with the two, as they can sometimes be 100 or so minutes apart when the geometry is right and Mercury is separated enough from the Sun; that won't happen this time.  However, the declination gap between the two is good right now, meaning that for several minutes of darkness, brightening Mercury will be easy to see for well over half an hour low to the horizon.