The Elongated Mercury

   This evening the waxing crescent Moon and three planets will be above the western horizon at sunset, however depending on your latitude and shape of your local horizon Mercury and Saturn may be a challenge to see. Adding to that is at the time of sunset the sky is still too bright to see these planets with the naked eye. And by the time the sky darkens enough, maybe another 20 minutes or so, Mercury and Saturn may have already set.

Mercury at Elongation

9 October: Mercury at Greatest Eastern Elongation

   The Planet Mercury has reached the point in its orbit around the Sun where it is at its maximum angle out from the Sun as we see the two of them from here on Earth. This is known as an elongation. Since Mercury is currently on the left or east side of the Sun it is an ‘evening planet’ setting after the Sun, and today it is at its Greatest Eastern Elongation.
   Not one to stop, Mercury continues moving until reaching greatest western elongation at the end of next month. Until then the innermost planet will be moving in retrograde or toward the west. As Mercury moves west at the rate of about 4 degrees each day the Sun in its apparent motion toward the east is moving about 1 degree each day. So in less than a month, on 1 November, Mercury will have reached inferior conjunction, between the Sun and Earth.

   
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

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