The elusive little planet Mercury has begun its apparition as a morning star following its inferior conjunction between Earth and Sun on 2010 SEP 03. The morning celestial geometry is favorable at this time of year for observers north of the tropics, while poor for those located south of the tropics.

I’ve created diagrams illustrating Mercury’s entire current morning apparition as observed from Chicagoland and Sydney. However, they should well serve most observers in the respective hemispheres. They can be seen by clicking: http://www.curtrenz.com/astronomical then going to the page for the Inferior Planets.

All dates given here are based on CDT (UT-5). Mercury will reach its greatest western elongation of 17.9° from the Sun on SEP 19. It will attain its greatest altitude at 30 minutes before sunrise from Chicagoland on SEP 20 at 10.8°. On that same date it will achieve dichotomy (50% illuminated like a Half Moon). Before that date it will be a crescent and afterward gibbous. While increasing in brightness, it will then fall to superior conjunction behind the Sun on OCT 16.

Mercury will pass 5.6° south of Regulus on SEP 13. During this apparition there will be no other conjunctions by Mercury near first magnitude stars, planets or the Moon while away from the glare of the Sun.

Photos and descriptions of Mercury’s morning apparition would be welcome additions to this thread.