Southern Colorado Skies / May 20-26, 2018

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


As noted below, on Sunday evening one of Jupiter’s moons, Ganymede, will transit (cross in front of) the face of Jupiter. This a relatively common occurrence that is visible even in telescopes as small as 90 mm, although a 6-inch or larger telescope is recommended along with excellent seeing conditions.

You can observe three separate parts of this event. First, because of the Sun’s angle at this time, Ganymede will pass in front of the planet – this is indicated in the following graphic by a dotted gray circle. Be patient – the moon may be difficult to see.

Easier to see will be Ganymede’s dark shadow as it follows behind the actual moon. The shadow will be visible at the same time as the moon and then by itself as the moon moves off to the right.

Sunday (May 20)

You can enjoy some activity at Jupiter tonight. Ganymede, Jupiter’s largest Galilean moon, will cross the gas giant’s surface from 10:07 to 11:26 p.m. MDT. It will probably be easier to see Ganymede’s shadow cross from 11:05 p.m. to 12:50 a.m. MDT. See the above graphics for an explanation of this phenomenon.

Monday (May 21)

First-quarter Moon at 7:49 p.m. MDT.



Mercury (in Aries)

Hidden in the Sun’s glare this week, but it may be visible with binoculars about 20 minutes before sunrise low on the eastern horizon. If you have a look, be careful of the rising Sun!

Venus (in Gemini)

Look for Venus above the west-northwestern horizon shortly after sunset. It’s now almost as high as it will be until the end of summer. It’s near the ‘feet’ of Gemini (see above graphic).

Mars (in Capricornus)

Mars rises just after midnight and is in good viewing position well before dawn. Look for Mars to the lower left (east) of Saturn.

Mars is abnormally bright now, but it will be getting brighter over the next few months as it gets to opposition (on a line extending outward from the Sun through the Earth) in late July. At that time Mars will be brighter than at any time since 2003, and almost twice as bright as Jupiter. See my article in the May Southern Colorado Skies, a link to which is included with this e-mail.

Jupiter (in Libra)

Jupiter appears in the southeast during twilight and dominates the sky (except for Venus) for the rest of the night. It was at opposition on May 8th but is still bright and big. The best views through a telescope or binoculars will be near midnight.

Saturn (in Sagittarius)

Look for Saturn above the Sagittarius “teapot.” The ringed planet will rise about an hour after dark, and will be at its highest elevation in the south at dawn.

Uranus (in Pisces)

Lost in the glare of the Sun.

Neptune (in Aquarius)

Look low in the southeast just before dawn.


The following data are based on my location in Pueblo West, Colorado. If you live well outside this area, you should consider checking this information for your location in order to be assured of accurate times, elevations, etc. If you’re unfamiliar with Iridium flares, check out my short article at:

Monday (May 21) 4:41:56 a.m. / Magnitude -1.6 / WSW / Elevation 63 degrees

Tuesday (May 22) 9:34:14 p.m. / Magnitude -1.0 / NNW / Elevation 11 degrees

Thursday (May 24) 2:53:59 a.m. / Magnitude -2.3 / WNW / Elevation 29 degrees

Thursday (May 24) 4:28:46 a.m. / Magnitude -5.4 / WSW / Elevation 59 degrees


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

Carpe noctem

Dave Furry
Pueblo West, Colorado

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