Star Calendar – May 2017

Star Calendar

May 2017

Start Calendar Planets:

Moon and Sun each elongate the fluid earth and exert tidal stress on the viscous and solid earth. This stress and shape distortion moves around the longitudinal earth in the two periods 12.42 and 12 hours respectively but also change latitude (declination) according to each body’s characteristic seasonal movement. Proximity of each body further modulates the effect. We then have a complex combination of rhythms and directions of tidal stress/distortion which serve to enhance and diminish each other. But the world is not covered evenly in fluid – there are instead basins and channels of various size that the generated tidal wave must negotiate. The size, orientation and capacity of this complex serve to also generate resonances and nodes so that local expressions of these stress inputs can appear sensibly aligned or apparently out of phase, greatly enhanced or diminished. The largest noticeable rhythm in most instances is the M2 tide (Moon tide at twice its diurnal frequency), modified by its phase with the lesser S2 tide. Out of phase is called “neap”, in phase is called “spring” and these alternate roughly every week. This is further modulated by apo/perigee, and then by ap/perihelion. The greatest Spring tide would occur if perihelion were to occur at an equinox (not for 5000 years or so) and perigee. These latter factors can be overwhelmed by local weather; atmospheric pressure bulges and winds.

Mercury makes a poor, shallow morning apparition this month. He skulks well below an already low ecliptic for his elongation.

Venus stands farther afield the Sun, and much less south of the morning ecliptic than Mercury. All month she will be easily mistaken as a distant airplane in the east before dawn.

Sun passes over Spring Valley 3 minutes 49 seconds before it reaches the time zone meridian of 75W. A lesser peak of the equation of time (published for the time zone meridian) renders clocks 3 minutes 41 seconds slow on the 13th this month. The two effects will make sundials agree with clocks at the middle of this month – excepting the silly discrepancy of the DST hour.

Mars is dimmer and to the right of Aldebaran, barely discernible as evening darkens in the early part of this month. Aldebaran subsequently drops from view much more quickly than Mars, overtaken by the Sun by Month’s end. Mars is not overtaken (conjunct) until July 27th – but is also un-viewable long before then.

Jupiter is now past opposition but also is more dominant in the evening since he is appearing higher as night falls. On the 1st he is 30 degrees in the SE at Nautical Twilight. On the 31st he is 45 degrees and South (culminating) at Nautical Twilight.

Saturn still rises very late and low – is really only noticeable to very early risers. He is quietly preparing for his opposition in June – but due to the wintry region he occupies, this will mostly be obscured by foliage and other ground clutter.

Star Calendar Days

1      Sunrise/set in Spring Valley at 5:59/19:53 (13h54m daylight)

        May Day (Beltane) celebrates beginning of cross-quarter Summer

        Mars, Sun and Saturn are in syzygy (fall on a line in space)

 2     Mercury is stationary to stars, now moves in normal (leftwards) motion

 3     Moon to right of Regulus, South as evening darkens

 4     Moon to left of Regulus, South as evening darkens

 5     Martian equinox, Spring for northern half.

 7     Moon beside Jupiter and above Spica in SSE as evening darkens

10     Full Milk Moon at 5:42PM, is apogee and in Libra

13     Equation of time makes SV sundials agree with clocks today

17     Mercury at largest (but shallow) angle from Sun for this appearance

22     Moon and Venus a fetching pair for early risers, East at 4:30AM

25     New Moon and Perigee, large amplitude Spring Tide

27      Mars below and to right of Moon shortly after 9PM WNW

30-31 Moon passes Regulus – look West each night around 10PM

31       Sunrise/set in Spring Valley at 5:26/20:22 (14h56m daylight)

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