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The night sky in July

Since Mars and Jupiter are just returning to our skies from their respective vacations behind the Sun they are only viewable in the predawn sky

On July 3, the planet Venus appeared low in the west at evening twilight against the backdrop of the Beehive open star cluster, in the constellation Cancer.

On July 6 watch for a waning crescent Moon about 3 degrees below Mars and 7 degrees  below Jupiter, just above the eastern horizon in the predawn twilight. The Moon is new, beginning another lunar cycle at 1:14 am on July 8 and then on July 10 just after sunset, watch for the waxing crescent Moon 7 degrees below Venus.

One of the notable events of the month is set to occur July 15 when the first-quarter Moon will be about one third of a degree off Virgo’s brightest star system Spica, very low in the west-southwest just after sunset. The angular separation between the Moon and Spica on that date will be about equal to that of two thirds of a full Moon. The day following has the waxing Moon about 4 degrees below Saturn low in the southwest in the early evening.

Another notable event takes place in the early evening of July 21, when Venus is just over one degree above Regulus, the brightest star in Leo, which is just above the horizon to the west-northwest. Since Mars and Jupiter are just returning to our skies from their respective vacations behind the Sun they are only viewable in the predawn sky. On July 22 Mars will be less than one degree above Jupiter over the eastern horizon at their closest approach, as Jupiter passes Mars to be higher in our sky. The Moon will be full later that day at 12:16 pm PDT.

Toward month’s end, on July 28, the South Delta Aquariid meteor shower will reach its peak activity in the predawn hours, with perhaps 15 – 20 meteors per hour. More will be mentioned on meteor showers in the article for August, the month which showcases the Perseid meteor shower. Generally meteors can appear anywhere in the night sky but if one traces back the path of any South Delta Aquariid meteor it will look to have come from the constellation Aquarius and closest to the third-brightest star of that constellation, Delta Aquarii.

July concludes on a planetary highlight, as Mercury will be at its greatest western elongation on July 30, raising it the furthest above the eastern horizon in its orbital cycle, and 20 degree west of the Sun at its greatest separation from the Sun before sunrise. Thus Mercury will be below Mars and Jupiter in a trio of predawn planets on that date.

Readers of this article should note that over the summer the Royal Astronomical Society will not be meeting, but those interested in star gazing are welcome to drop by the astro-cafe at Pier 17 on Friday, July 19 where some of the local club members will meet at 8:30 pm for coffee and to chat about all things astronomy. If it is clear, a couple of telescopes will be set up nearby for viewing the sky after sunset. More info at www.CoastAstron

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