December Moon at Perigee

   Our Moon reaches perigee, (closest distance to Earth), for this orbit, on Wednesday December 18th. At that time the Moon will be at a distance of 26.025 Earth diameters, 230,069 miles (370,260 km) from the Earth.

   On the day of the perigee Moon the 22-day old waning gibbous Moon will be over the south-southwestern horizon at sunrise local time. The planet Mars is also visible over the southeastern horizon. If your local eastern horizon is low enough then the innermost planet, Mercury, might be seen near the reddish star Antares in Scorpius the Scorpion.

   Does our Moon actually go around the Earth as this graphic shows? From our perspective on the Earth the Moon appears to circle around the Earth. However, in reality, the Moon orbits the Sun together with the Earth*
   *Click here to read my 2006 Scope on the Sky column “The Real Shape of the Moon’s Orbit”. (PDF)

   
   
   

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A Couple of Morning Planets

   Early chilly mornings yes, but two planets are visible before the Sun rises. Maybe seeing Mars and Mercury will make it worthwhile? They are both within the realm of the constellation Libra the Scales. As a bonus Dwarf Planet Haumea is also above the horizon but with an apparent magnitude of 17.0 it is virtually invisible without some optical assistance.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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A Pair of Conjunctions

   Sunday November 24th there will a photo or viewing opportunity during the twilight hour before the Sun rises and after the sun has set. Starting off the day will be a conjunction involving the very thin waning crescent Moon near the ‘Red Planet’ Mars. The two will be separated by about 3-4o. Lower or to the east is the innermost planet Mercury.
   Then, approximately 12 hours later, the Sun has or is about to set and over the western horizon is a cluster of 3 planets. Close together and separated by about 1-2o are the planets Jupiter and Venus. Higher or to the east is the planet Saturn.
    Both of these conjunctions will look great through binoculars or a wide-field eyepiece on a telescope, and obviously will make for interesting pictures.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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Visualize the Ecliptic

Above the Terrestrial Planets this Month

   Once in a while the planets are arranged such that they are spread across the sky. The planets are not lined up in a straight line outward from the Sun but rather are arranged along the ecliptic. The ecliptic is the Earth’s orbital path around the Sun and the respective orbit of each planet is inclined from the ecliptic. And this is one of those times when it is easier to visualize the ecliptic. (see graphics below) Click here to read a previous posting about the ecliptic and planet inclination.

   As the animated graphic is showing the terrestrial planets are not arranged in a straight line. This graphic shows the solar system out to Neptune and from this perspective the planets are obviously not in a straight line.


   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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November Moon at Descending Node


   Friday November 1st the Moon will be crossing the plane of the ecliptic moving south. This is known as the descending node, one of two intersections the Moon’s orbital path (dark green line) has with the ecliptic.

   On the day of the node crossing the 5.0-day old waxing crescent Moon will be over the southwestern horizon and will be about 3-4o to the west from the ringed planet Saturn. By Saturday evening, the 2nd, the Moon will have moved to the east of Saturn and will be about 8o from Saturn. Jupiter shines brightly further to the west. However with a more level horizon the two inner planets Mercury and Venus are visible. And with binoculars or telescope the Dwarf Planet Ceres could be seen about 3-4o from Jupiter.


   
   
   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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Two Conjunctions this Evening

   Thursday evening October 31st look toward the western horizon but not for trick or treaters. Rather look for the two inner planets to be within about 2-3o from each other, and a bit further eastward for the Moon to be about 4-5o from Jupiter. Also the Dwarf Planet Ceres is within 3-4o from the crescent Moon. However Ceres is at 8th as compared with Jupiter at -2.0 and the crescent Moon at -11.0 apparent magnitudes. And before anyone asks Venus is at -3.9 and Mercury at 0.63 apparent magnitude.
   Each of the pairs will easily fit within the field of view of binoculars.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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Crescent Moon Near Venus and Mercury

   Tuesday evening October 29th a very thin 2-day young waxing crescent Moon will be about 4-5o from the two inner planets Mercury and Venus. All three will easily fit within the field of view of binoculars – however be careful as they are not that far from the setting Sun.

   Over the next several days as the Moon waxes toward first quarter phase the Moon will pass by the Dwarf Planet Ceres and the outer planet Jupiter and then Saturn.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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