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The Sky This Week, 2015 March 3 - 10

Daylight Time is upon us! (Please don't shoot the messenger)
Jupiter with Ganymede and its shadow, 2015 March 3, 02:34.5 UT

A bright Moon beams down during the overnight hours, brightening the still snow-covered landscape as we head into the first full week of March.  Full Moon occurs on the 5th at 6:05 pm Eastern Standard Time.  The March Full Moon, popularly known as the Worm Moon, Crow Moon, or Sap Moon, holds a slight promise of stirring in the thawing ground and awakening trees, indicating that spring is inexorably on the way.  Luna starts the week near the bright star Regulus in the constellation of Leo, the Lion, then wends her way through the sprawling constellation of Virgo.  She passes close to the bright star Spica on the night of the 8th and 9th before diving into the southern reaches of the ecliptic and the rising stars of early summer. 

The arrival of the second Sunday in March means that it is once again time to set our clocks ahead by one hour to begin observing Daylight Time.  This annual exercise has never been a particularly popular one for many people, especially those who live on the western boundaries of time zones.  Folks who live in these areas will find themselves waking up in near total darkness for several more weeks in exchange for more daylight in the afternoon hours.  The idea behind it has been attributed to Benjamin Franklin, who wrote a satirical essay on the subject while he lived in Paris in 1784, but the first real attempt to implement it came about at the turn of the 19th to the 20th Century.  First proposed by New Zealander George V. Hudson in 1895, the cause was taken up by Great Britain’s William Willett in 1905.  One of Willett’s reasons for shifting the clocks was his desire, as an avid golfer, to have his after-work round unhindered by sunset and the onset of darkness!  He lobbied members of Parliament for some 10 years, initiating a series of hearings and studies on the time-shift’s benefits and drawbacks.  Willett died in 1915, but in the following year World War I brought the issue to a head.  The Germans and their allies established the change, followed quickly by the rest of the European nations as an effort to conserve coal used to generate electricity to light factories.  The U.S. adopted the idea in 1918 as an incentive to help factory workers tend their “victory gardens” after their day shifts.  However, it wasn’t a popular move, and national standards for it were abandoned in 1919 and weren’t re-established nationally until 1966.  Since that time the rules have been changed by presidential or congressional action.  The current scheme is the result of the Energy Policy Act of 2005.  Here at the U.S. Naval Observatory, while we provide the basis for precise timekeeping for the nation, we have nothing to do with how folks use it.  The agency responsible for enforcing the Act is the Department of Transportation, so please call them if you have complaints!  And don’t forget to “spring forward” one hour at 2:00 am on the 8th!

The one advantage to Daylight Time that I can see is that it gives us more time to get ready for the evening’s stargazing adventures.  For the next several months I can now grace the dinner table and enjoy my supper before going out to the telescope.  This will also mean that I can finally observe Venus at a reasonable hour before she slips behind the trees.  You should have no trouble finding her in evening twilight, and once we’re on daylight Time she’ll linger in the west until around 9:30 pm.

Daylight Time also seems to give Jupiter a bit of extra time for study.  He’s been steadily creeping up to earlier meridian transits (when he’s highest in the sky), but starting on the 8th those transits will occur an hour later by clock time.  This puts him back in the “sweet spot” for my home observing site for longer periods and will be especially handy when the leaves start filling out in the nearby trees.  Jupiter is now a month past opposition, so his visible disc is beginning to slowly shrink.  Fortunately the planet is large enough that this doesn’t make a huge difference in his appearance, and his major weather features and bright Galilean moons should continue to provide entertainment to telescope owners until the summer months.  The main effect of being past opposition is seen when the moons transit the planet’s disc and cast their shadows; the moons now lead the umbrae as they march across the planet’s face.  You can watch Io enter the disc on the evening of the 3rd at around 9:20 pm EST followed by its shadow about 40 minutes later.  On the evening of the 9th Ganymede begins to transit the planet at around 9:00 pm EDT; its shadow follows it just over three hours later!

The change to Daylight Time means that most of us will now be waking up in the dark.  While I am by no means a “morning person”, the one consolation I have is that I won’t have to get up at 5:00 am to see Saturn.  The ringed planet will now cross the meridian at around 6:00 am just as morning astronomical twilight begins.  I’ll have an hour to peruse him before the sky gets too light and it is time to fix breakfast.



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