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 – May, 2016

Star Calendar

May, 2016

Star Calendar Planets:

Moon is Full three, or sometimes four, times in a season but the names that various cultures have assigned to characterize the circumstances around various full moons of the year generally number 12 – leaving the occasional unnamed one. Similarly the Hebrew luni-solar calendar has 12 months – but needs to insert an inter-calary month about every three years to maintain its relationship to the solar year. In each case the adjustment occurs 7 times in 19 years – the extra full moon is called Blue and the extra Hebrew month is called second Adar. This month’s full Moon coincides with the opposition of Mars – and the latter will shine in the very spot towards which falls the shadow of the Earth – so on the night of the 21-22nd one can easily see just how far the moon is from being eclipsed.

Mercury promises to be visible in broad daylight on the 9th. Inferior conjunction will cut right across the face of the Sun, beginning somewhat after sunrise, midway around 11 and leaving in mid-afternoon. One can observe this with a camera obscura arrangement that projects and enlarges the disk of the sun onto a screen. I might cover a south or SE-facing window and allow a pinhole of light through a piece of aluminum foil to cast onto a sheet of white cardboard. Such a transit of Mercury last occurred ten years ago – but these are far less rare than transits of Venus – which I will never see again.

Venus is lost in morning limelight as she heads backstage for some future showing in evening attire.

Sun is midway from equinox to solstice on the 1st. Astronomically this marks the beginning of Summer, the solstice being regarded as mid-summer. The days are now getting longer much more slowly – by about one minute a day as the month opens and only 30 seconds a day as the month ends.

Mars makes a large retrograde stroke and rises dramatically earlier over the course of this and next month. He breaks the horizon at about 9 PM on the 1st and already at 6:18 by the 31st.  This opposition is the nearest for Mars since the superlative one of ten years ago. But, due to Mar’s high degree of ellipticity, he will continue to draw nearer for another week after opposition, then being twice as near to us as is the Sun (.5AU).

Jupiter finally diminishes perceptibly from its late brilliance but still dominates the evening sky in the south. Mars will match magnitude during its opposition- but rises later and culminates much lower – achieving only the altitude of the Sun at mid-winter.

Saturn is also in a retrograde loop, one much smaller than Mars’, and rises just under an hour later. Saturn is then seen to be about as bright as Arcturus – but shining with a steady light compared to the latter’s yellow-green scintillation. Saturn will reach opposition on June 3rd.

Star Calendar Days:

  1      Sunrise/sunset in Spring Valley at 5:53/19:54 (14h1m daylight)

          First day of cross-quarter-wise summer, Beltane

  6      New Moon 15 hours after perigee, again large spring tides

  8      Moon to right of Betelgeuse and above Aldebaran, WNW around 9:PM

  9      Mercury crosses face of Sun (transit) begin 7:12-max 11:-ending 2:40

          Jupiter stationary to direct motion, ends it’s loop for this year

13      Moon next to Regulus, SW as dark falls

14      Moon next to Jupiter, SSW as dark falls

18      Moon beside Spica, SE as dark falls

21      Full Blue Moon at 17:14 (This season has 4 Full Moons, the 3rd is “Blue”

          Mars rises (in the exact direction of Earth’s shadow) beside the Moon, ESE 8:30PM

          Mercury stationary to direct (leftwards motion against stars)

22      Mars in opposition 7:AM, 14 hours after Full Moon

          Moon rises to left of Saturn, SE at 10:PM

30      Mars is nearest Earth, half as distant as is the Sun

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

Star Calendar – May, 2015

Star Calendar

May 2015

Star Calendar Planets:

Moon marks the vernal equinox point as it rises 4-5 AM as a waning crescent on the 14th. On the 20th the Moon crosses the summer colure (but somewhat below the ecliptic) and one can then see/feel how far it is to summer after sunset on that evening. On the 27th the Moon sits just about exactly on the fall equinox after sunset.

Mercury is highest for this evening appearance on the 7th, but is also already getting dimmer. He is stationary to stars, beginning retrograde motion, on the 19th and in only 8 days overtakes Mars in their race toward the Sun. Mercury crosses in front of Sun on the 30th and will make a poor morning appearance in June.

Venus continues to be seen slightly higher and brighter each evening this month. The Moon makes a nice enhancement on the 21st as she approaches a fetching alignment with Pollux and Castor of Gemini – coming in early June.

Sun movement along the ecliptic is slowing down, bringing meridian crossings (solar noons) closer together (shortening the interval of the whole day). At the same time there is an increasing advancement of the Sun’s equatorial-coordinate movement each day (lengthening the whole day interval). The latter factor overtakes the former in magnitude on the 14th of this month – see Equation of Time below. It is odd that the cross-quarter of the seasons (here, the midpoint between vernal equinox and summer solstice, on April 30) just about coincides with the 1/3 point of our Roman calendar year, on May 1.

Mars (unobservably) approaches the Sun with stealth and will creep around and behind in mid-June.

Jupiter stands halfway to the zenith in the WSW after sunset. To the left, and somewhat higher, is Regulus, the heart of Leo. The pair will slowly converge and appear lower each evening – their accomplished meeting in August then being obscured by proximity to the Sun.

Saturn is in opposition and up all night, rising below the much higher Arcturus in the evening. Saturn, now at maximum brightness, just about reaches “zero magnitude”, which is defined as the brightness of the star Vega (to be seen further to the NE these evenings). Vega is the brightest star of our summer sky. Continue reading