Sky Notes for 19th-22nd July 2008
Saturday 19th July 2008
Mars is 4.8° to the upper left of Saturn. Look for both planets in the west in the evening twilight. This is the last chance to see both planets within 5° of each other. Mars and Saturn are moving away from each other and dropping closer to the western horizon each night. The star Regulus is 6.7° to the lower right of Saturn.
Sunday 20th July 2008
Regulus, Saturn and Mars span 12° in the western evening sky. Look for the three objects in a diagonal line across the sky. Regulus is to the lower right. Mars is to the upper left. Saturn is in the middle. Look about 1 hour after sunset. Saturn is the brightest of the three, shining at 0.8 magnitude. Much brighter at -2.6 is the planet Jupiter in the southeast sky at the same time.
Monday 21st July 2008
The waning gibbous Moon rises in the east near the end of astronomical twilight. The end of astronomical twilight is defined as the time when the Sun is 18° below the horizon. After the end of astronomical twilight, the sky is as dark as it’s going to get. Not counting light pollution from cities, towns and the Moon. Civil and nautical twilights end when the Sun is 6° and 12° below the horizon. During nautical twilight the sky is dark enough to see most of the brighter stars and planets but not the dimmest stars visible in the night time sky.
Tuesday 22nd July 2008
The globular star cluster M-13 is high overhead this evening. M-13 is located in the constellation of Hercules. With binoculars, M-13 looks like a fuzzy star. Through a telescope, the star cluster appears as a swarm of faint stars in the shape of a ball. M-13 is about 25,000 light-years from the Earth. This cluster was discovered by Edmond Halley of Halley’s comet fame in 1714.
The 22nd of July is also Pi Approximation Day!
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