This Week's Sky at a Glance July 23 – 31

This Week's Sky at a Glance
Some daily events in the changing sky for July 23 – 31.
by Alan M. MacRobert
Fourplanets shine in the western twilight. One dazzles; the others appeartiny by comparison. Watch them changing positions day by day! This istheir arrangement at week's end. (The visibility of faint objects inbright twilight is exaggerated here.)
Sky & Telescope diagram
Friday, July 23
Saturn's wild, weird moon Titanis at western elongation from Saturn this evening. Most amateurtelescopes will show it (at 9th magnitude). Follow Titan as it swingsback and forth in orbit around Saturn every 16 days!
Saturday, July 24
A line drawn from Deneb,high in the east, through Altair, not quite as high in the southeast,points down nearly to the Moon this evening.
Jupiter'sGreat Red Spot transits Jupiter's central meridian around 2:48 a.mSunday morning Eastern Daylight Time; 11:48 p.m. Saturday eveningPacific Daylight Time. See our list of all theGreat Red Spot's predicted transit times, good worldwide, for the rest of 2010.
Sunday, July 25
Full Moon (exact at 9:37 p.m. EDT).
Monday, July 26
As the stars begin comingout in the evening this week, Arcturus shines high in the west, far tothe upper left of bright Venus. Watch the Big Dipper glimmer into viewequally high in the northwest, far to Venus's upper right.
Tuesday, July 27
Regulus is now less than½° upper right of brighter Mercury low in the sunset glow. Usebinoculars to look for the two a half hour aftersunset. They're well to the lower right of brighter Venus.
Wednesday, July 28
Big Hercules remainshigh in the evening sky. Maybe you're familiar with its globular starclusters M13 and M92. But what about its bright Turtle Nebula, NGC 6210,or the faint galaxy NGC 6269 amid a cluster of even fainter companions?See Ken Hewitt-White's "Going Deep" article and maps in the JulySky & Telescope, page 63.
Thursday, July 29
Mars is less than 2° below slightly brighter Saturn at dusk, as shown at right.
Friday, July 30
Mars is still less than 2° below Saturn at dusk.
Jupiter rises roughly 6° lower right of the waning crescent Moon around11 p.m. daylight-saving time (for skywatchers in North America).
Saturday, July 31
Saturn and Mars remainclose together upper left of Venus at dusk, as shown at the top of thispage. Use binoculars to try for Mercury and especially Regulus muchfarther to Venus's lower right.