SCAS – Southern Colorado Skies / December 6 – 12, 2015

Consider a planetarium program to help you plan your observations. There are many commercial products available, and a very good program (Cartes du Ciel) is available free at


Monday (December 7):

The Moon occults (appears in front of) Venus during daylight hours for almost all of North and Central America. The Moon will be a very thin crescent phase located about 43 degrees west of the Sun. The occultation will begin with Venus disappearing behind the Moon’s illuminated limb, and end with Venus reappearing behind the Moon’s dark limb. This event should be visble using bimoculars or a small telescope. (BE CAREFUL NOT TO POINT YOUR INSTRUMENT OR LOOK DIRECTLY AT THE SUN!) The closest Pueblo times for the occultation that I could find were for Denver, which shouldn’t be too far off:

Occultation begins: 9:35 a.m. MST
Occultation ends: 11:12 a.m. MST

Tuesday (December 8):

The earliest sunset of the year (for our latitude) occurs today. But wait! – why isn’t the earliest sunset on winter solstice, the shortest day of the year? Solstice won’t occur for a couple more weeks!250px-Sunset_2007-1

The reason is the discrepancy between your clock and the Sun’s path across the sky (also known as the Equation of Time, which tracks the difference between mean solar time and apparent solar time). On a clock, from one noon until the next is exactly 24 hours (‘mean solar time’), but due the elliptical orbit of the Earth’s orbit around the Sun this doesn’t always correspond to apparent (or ‘true’) solar time – which is the time that would appear on a sundial. The date of earliest sunset is also due to the Earth’s tilt, which causes these dates to vary by latitude – some locations on Earth won’t experience their earliest sunset until later this month!

Sunset today occurs at 4:38 p.m. in Pueblo, but on the solstice the sunset will occur three minutes later at 4:41 p.m. More information on this interesting topic may be found at

Saturday (December 12):

The Geminid meteor shower won’t reach its peak until early next week, but it should already be spewing out meteors. The best time to observe is after midnight, as Earth will be turning into the shower at that time.


Mercury (in Scorpius):

Lost in the glow of the Sun.

Venus and Mars (in Virgo) and Jupiter (in Leo/Virgo):

Still-bright Venus keeps company in the pre-dawn eastern sky with Mars and Jupiter, with Mars between widely-separated Venus and Jupiter. Venus will be occulted by the Moon on December 7th – see above.

Saturn (in Scorpius):

Hidden by the Sun.

Uranus (in Pisces):

High in the southern sky by early evening.

Neptune (in Aquarius):

High in the southern sky by early evening.

Iridium Flares and International Space Station (ISS)

Sorry – these are too numerous to list here! If you’re serious, load the ISS DETECTOR app on your smart phone or tablet. Alternatively, refer to SCAS member Chuck Percival’s column in the Sunday Pueblo Chieftain.

Have fun!

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