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In Search of the Lost Hour

by Geoff Chester, USNO Public Affairs | 05 March 2024

by Geoff Chester, USNO Public Affairs | 05 March 2024

The Rising Dipper in moonlight, 2019 February 19
Imaged from Mollusk, Virginia with a Canon EOS Rebel SL2

The Moon moves from the morning into the evening sky this week, greeting early as a slender waning crescent before vaulting into evening twilight by the week’s end.  New Moon occurs on the 10th at 5:00 am Eastern Daylight Time.  

Yes, you read that correctly.  This is the week when we advance our clocks by one hour to adjust for Daylight Saving Time.  Technically this occurs at 2:00 am local time on the 10th for almost all residents of the U.S.  The exceptions are people who live in Hawai’i, where the annual variation in the length of daylight amounts to just over 2.5 hours between winter and summer, and Arizona, which opted out of observing it after 1967.

Daylight Time has been a controversial topic since Congress first implemented it in 1918.  One of the “selling points” for advocates was that later sunsets would give factory workers time at the end of the day to tend their World War I victory gardens.  The time change was so unpopular that Congress repealed the rule in 1919, leaving the observance up to individual states to observe.  The next Uniform Time Act, enacted in 1966, once again mandated national observance of Daylight Time with the option for states to opt out.  There were various adjustments in the dates of Daylight Time, but today’s rules are the result of the Energy Policy Act of 2005. 

The March campaign for the Globe at Night citizen science program continues this week until the return of the Moon to the evening sky on the 11th.  This international program aims to increase awareness of the night sky by engaging people to count stars visible in familiar constellations.  This month we’re counting stars in Orion, which lies just west of the meridian at the end of evening twilight.  Orion is a great target since it is easily visible from all inhabited parts of the planet.  His outline is as prominent in urban skies as it is under desert vistas.  This is your last week to view him in the early evening.  Daylight Time pushes the end of evening twilight to 8:45 pm.  Report your observations using the Globe at Night web app.

As Orion and his bright companions slide westward in the late evening, the more subdued stars of spring become more prominent in the east.  Among these is a seven star asterism that is almost as well-known as Orion’s belt stars.  This distinctive figure, which is popularly known as the “Big Dipper” to most of us, stands high in the northeastern sky by 9:00 pm.  The Dipper is also known as “The Plough” in British folklore and “The Wain” (wagon) in Germanic traditions.  The Dipper can be seen under relatively bright suburban skies, but if you venture to darker locations you will see that it is part of a larger constellation, Ursa Major, the Great Bear.  

Five of the stars in the Dipper are related, moving together through space at distances of 78 to 84 light years.  The stars that mark the lip of the “bowl” and the end of the “handle”, Dubhe and Alkaid, respectively, are more distant and are moving in different directions from the main group.

Under careful scrutiny you will find that the star that forms the bend in the handle, Mizar, has a close companion visible to the naked eye.  This star is Alcor, and resolving the pair has long been a test of visual acuity.  It has been said that recruits for the Roman legions needed to prove their eyesight by seeing it.

If you look at Mizar with a small telescope, it will resolve into two components.  It is often one of the first double stars that new telescope owners view.  Each component of the apparent double is itself a spectroscopic binary, as is Alcor, making the Mizar-Alcor system the closest six-star system to us.

Jupiter continues to shine in the early evening western sky.  The giant planet is still the brightest object to see during the first hours after sunset, but he drops a bit lower each night.  By the end of the week Old Jove sets at around 10:20 pm.  He gets something of a reprieve after the switch to daylight time, delaying his departure by an hour.  That said, the best time to view him in the telescope is in twilight when he is still relatively high above the horizon.

Venus rises about an hour before the Sun, so she is now only visible in brightening morning twilight.  You should try to locate her half an hour before sunrise, but she will only be a few degrees above the horizon.  


Commander, Naval Meteorology and Oceanography Command | 1100 Balch Blvd. | Stennis Space Center, Mississippi 39529

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