Star Calendar – April 2016

Star Calendar

April 2016

Star Calendar Planets:

Moon is very dynamic and has several motions of similar mode. A Frenchman sewed photographs of sequential Full Moons together into an animated GIF that shows very nicely the net effect of the various librations – the nodding and swaying face and changes in proximity in a kind of slow stroboscopic form. The next-to nearest perigee for this year coincides pretty closely to New Moon this month – the waters will respond. Of note; the center of mass of the Moon is well displaced from its geometrical center. This lopsidedness is probably why we see only one side of the Moon – its center of mass prefers to be toward the earth.

Mercury is an evening star all this month. With a good view to just North of West one might find him to the right of a thin Moon around 8:15 PM on the 8th. Thereafter he will be higher until the 18th, then seen below the Pleiades as late as around 9PM.

Venus is now difficult to view in the morning. With a very good East horizon try to look to the left of the Moon on the 4th at 6:10 AM – Venus will next appear some evening in latter July.

Sun is not a point of light – rather a disk of ½ degree or 1/720th the circumference of the sky. Due only to this the Sun is visible above the horizon to slightly more than ½ of the planet at a time. In addition, the medium of air, increasing in density from empty space, bends the visibility of the Sun a further half-degree or so beyond the geometric-tangent horizon, trebling the effect. At any moment, roughly 50.4% of the Earth is in daylight. This has to do with why day and night are not of equal length on the equinox.

Mars approaches headlong this month and brightens dramatically. He does so near Antares (similar color but much dimmer) and Saturn, to his left. Recall that Mars and Saturn were of equal brilliance in mid-February – now look at the difference! Mars’ opposition is coming May 22nd. They are visible, low and southerly, between about 11PM and 5:30AM.

Jupiter appears much the same as last month, repeating a prominent pairing with the Moon on the night of the 17th.

Saturn makes a nice contrast to Mars and will be in its opposition on June 3rd, only 12 days after Mars’.

Star Calendar Days:

  1      Sunrise/sunset in Spring Valley at 6:39/19:22 EDT (12h43m daylight)

  6      Moon and Venus rise together – only with a perfect view east, at 5-5:10AM

  7      New Moon and very-near perigee only 6 ½ hours apart – spring tides

  8      Moon and Mercury set together – only with a perfect view west, at 8-8:30PM

10      Aldebaran emerges from occultation by Moon as they set; West, 8-11PM

12      Moon passes Alhena (foot of Gemini) WSW in evening

14      Moon makes a line with Pollux and Castor (heads of Gemini) SW in evening

16-17 Moon passes Regulus

17      Mars stationary to retrograde, brightening most rapidly now

17-18 Moon and Jupiter make a bright couple all night (like last month)

18      Mercury at largest angle from evening Sun for this appearance

20      Mars and Saturn nearest (no conjunction), visible SW11:30PM to SSW5:30AM

21      Moon setting with Spica WSW at 5:30AM

21-22 Full Sprouting Moon at 1:24 AM

23      Passover begins, the 15th of Nissan

24      Moon, Mars, Saturn & Antares rising together SE at 11:30PM

26      Mars, the brighter, nearest to Antares – of similar color; culminate S at 3:AM

29      Mercury stationary, to retrograde

30      Sunrise/sunset in Spring Valley at 5:55/19:53 (13h58m daylight)


1/3 of 2016 has passed; also midway from Spring equinox to summer solstice