SCAS – Southern Colorado Skies / September 18 – 24, 2016

Consider a planetarium program to help you plan your observations. There are many commercial products available, and an excellent program (STELLARIUM) is available free at


Besides contantly changing their relative positions, Jupiter’s moons (or, more technically, satellites) offer several interactions with the giant planet itself. As I report in this blog when Jupiter is visible, these interactions consist of occultations, transits, and shadows. 

Occultations occur when the moon passes behind Jupiter, as seen left-to-right in the first attached graphic. A transit is when the moon passes in front of Jupiter (the moon itself is essentially invisible). Sometimes a tiny shadow is cast on Jupiter’s surface from a visible satellite, and finally a shadow may be cast from a transiting moon.

















Sunday (September 18)

Look for Venus low in the west-southwest about 20 to 30 minutes after sunset. Spica (in Virgo) shines a couple degrees below Venus, but you will probably need at least binoculars to see it.

Thursday (September 22)

Autumn begins in the northern hemisphere (the Autumnal Equinox) at 8:21 a.m. MDT. The Sun (which defines the ecliptic) will be crossing the celestial equator heading south.

Friday (September 23)

Last-quarter Moon at 3:56 a.m. MDT.


Mercury (in Virgo)

Hidden by the glare of the Sun.

Venus (in Virgo)

Very low in the west-southwest about 20 or 30 minutes after sunset.

Mars (in Ophiuchus/Sagittarius)

Look how much farther Mars is to the left (eastward) and away from Saturn and Antares (below Saturn) than it was just a couple weeks ago! Look in the south-southwest at nightfall.

Saturn (in Ophiuchus)

NASA’s Cassini mission is finishing up its final year of exploration (click here for NASA press release).

Jupiter (in Virgo)

Now out of sight in the Sun’s glare.

Uranus (in Pisces)

High in the east southeast by 11 p.m. Uranus will be at opposition on October 15th.

Neptune (in Aquarius)

High in the south by 11 p.m. Neptune was at opposition on September 2nd.


Saturday (September 24): 05:29 a.m. / Magnitude -6.9 / SSE / elevation 61 degrees


These are too numerous to list here! If you’re serious, load the ISS DETECTOR app on your smart phone or tablet.

Have fun!

Dave Furry, SCAS Director of Education

SCAS rework Logo 3 Color copy

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