Star Calendar – April 2017

Star Calendar

April 2017

Star C alendar Planets:

Moon and Sun balance on either side of the solstice point on the 7th. They rise and set at the same point on the horizon on that day and make the same path across the sky. One might observe the pair at 4:45PM and imagine the height of summer between them.

Mercury begins the month at greatest elongation, bright and decently visible just after 8:PM or so. He is hasty to depart though, and crosses the near-side of the Sun on the 20th.

Venus is already visible in the morning and will be stationary to the stars by the 12th. She is very tall, waxing less slender and will present a maximally brilliant dawn beacon by the end of the month.

Sun rises/sets steadily more north of east/west and adds an hour and a quarter of daylight over the course of this month.

Mars is seen low in the West at about 7:30 as the month begins and lower and later as the month progresses. Mars and Aldebaran (higher and to the left) look very similar these days. On the evening of the 28th the Moon, Aldebaran and Mars will shine together WNW at about 7:45PM.

Jupiter reaches opposition on the 7th. He is now brightest and closest for the year and is in the middle of his period of backward movement near Spica. Look for the Moon in the mix on the 10th.

Saturn is seen culminating in the early morning and stops in the steam (Milky Way) of the Teapot (Sagittarius) on the 6th to begin this year’s loop.

Star Calendar Days:

  1      Sunrise/set in Spring Valley at 6:39/19:21 (12h42m daylight)

          Day number 91; ¼ of the year has passed

          Mercury shining in low West 8:PM, sets at 9:PM

          Moon in horns of Taurus in evening, West

  6      Saturn stationary, begins retrograde loop at spout of Teapot

          Moon passes close to Regulus during this night

  7      Jupiter at opposition, brightest and nearest for the year

  9      Mercury stationary, then retrograde to stars, already retreating Sunwards

10      Moon clusters with bright Jupiter and Spica, ESE in evening

10-11 Full Pink Moon at 2:08AM  (leaf buds are pink)

11      Passover begins

12      Venus stationary, to direct motion

16      Moon with Saturn in south at 5:30AM

          Easter

20      Mercury, so recently visible, at inferior conjunction

22-23 Moon and Venus present the same phase, East at 5:30AM, use binoculars

26      Venus most brilliant for this appearance

28      Moon strikes a pose with Aldebaran and Mars, around 9:PM, West

30      Sunrise/set in Spring Valley at 5:55/19:52 (13h57m daylight)

          More than 2 ½ hours additional daylight since March 1st

          Midway from equinox to solstice, and about 1/3 of year has passed

          Venus covers greatest sky area for this appearance

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

 

 

Star Calendar – April, 2015

Star Calendar

April 2015

Star Calendar Planets:

Moon and Sun cycles interacting generate the modern (Mainmonedesian) “lunisolar” Hebrew calendar. The calendar day begins just after evening civil twilight with the light and dark portions each then being divided into 12 hours. The month begins with the evening following New Moon. On seven occasions within a 19-year cycle of years an extra (intercalary) month is inserted to keep the normal months aligned with the seasonal solar year so that the year begins with the New Moon placed such that the following Full Moon (Nisan 15) occurs on or after the spring equinox. That Full Moon begins the seven days of Pesach or Passover. In the Gospels of Matthew, Mark and Luke, the Last Supper takes place at the beginning of Friday (! – n.b. EVENING begins the day!) Nisan 15. The crucifixion occurs during the following daylight hours (Good Friday) and Easter is the next Sunday. Various attempts to be faithful to, or emancipated from, various historical and/or astronomical aspects, or to regularize dates, have caused enormous complexities in defining the date of Easter. The fact is that Easter is a unique event – its historical/astronomical circumstances simply do not recur. So we might simply commemorate its spirit. Eastern churches use a 19-cycle formula for Paschal Moons, from Nicaea AD 325, to fix the date of Easter on the Julian Calendar. Western churches have gradually moved to the Gregorian Calendar, since AD 1583, and have an 84-cycle formula. Even when the two Easters occur on the same day – they’re still on different dates! Note that even a purely astronomical definition of Passover or Easter is troublesome since, due to time zones, world-wide astronomical events occur on two dates simultaneously!

Mercury crosses behind the Sun during the night of the 9th-10th.

Venus passes the Pleiades (aka “seven sisters”, one of which is called “Subaru” in Japan) during the second week of this month. Look west each evening between about 8:30 and 9PM.

Sun gave us a surprise wallop mid-March; resulting in some radio disturbances and intense Aurora.

Mars begins a three-month hiatus in the middle of this month and will reappear by mid-August.

Jupiter resumes direct (leftwards) motion amongst the stars on the 8th and begins to head for Regulus again. He will cross into the realm of Leo in early June and reach Regulus in August.

Saturn is now retrograde and will find its opposition in May. Saturn brightens much less dramatically than Jupiter. Continue reading