6degrees AstroBlog

Should We Move Boise to Pacific Time Zone?

By Irwin Horowitz, 5-29-07

June nights are short in the northern hemisphere.  The Sun sets later and rises earlier now than at any other time of the year.  The reason for this is that the Earth’s axis of rotation is tilted relative to the plane of its orbit at an angle of 23.°5 (about ¼ of the distance from pointing straight up to laying completely on its side), and in June the North Pole is pointed towards the direction of the Sun.  As you move further north from the equator, the length of nighttime decreases.  Indeed, on the summer solstice, the Sun doesn’t set at all for anyone located north of the Arctic Circle.  In contrast, we experience the opposite effects during December around the winter solstice.

What are the impacts of these annual cycles on amateur astronomers?  Well, it doesn’t take a rocket scientist to realize that the most enjoyable time to go observing is during the warm summer months.  In addition to the pleasant temperatures, the weather is generally more amenable at this time of year, as fewer storm systems cross our country in summer than in winter.  However, here in Boise we are often limited by the fact that it doesn’t get truly dark until nearly midnight.  When we hold public star parties, most of our audience is already packing up and heading home by the time the really interesting and fun stuff starts to become visible.

Contrast that with the lengthy nights we have in the dead of winter.  Sure, we can start observing before we’ve eaten dinner, but we are usually freezing our keisters before our telescopes are set up.  On clear winter nights it gets even colder, as the ground can cool off by radiating energy back into space.  We tend not to organize public star parties at this time of year because we recognize that you need a certain level of dedication (insanity?) to want to sit outside in sub-freezing temperatures to look at faint, fuzzy objects through your telescope.

So, how can we take greater advantage of the available hours under dark skies during the summer months?  How can we convince our audience at these public events to remain long enough to view the good stuff? 

First, we generally hold these events on Fridays and Saturdays, because people who attend don’t have to wake up early the next day to go to work.  However there still seems to be some subconscious programming that tells folks that when the clock strikes midnight it is time to go to sleep.  So what can be done to encourage our audience to stay long enough for it to get dark and we can show them some amazing views?  One possible solution, at least in western Idaho, would be to relocate us into the Pacific Time zone.

Time is a fascinating construct in modern society.  How we set our watches and clocks and timepieces is based on a broad range of issues, from geography to politics to economics and commerce.  The development of the modern system of timekeeping, with time zones and daylight saving, is a story filled with both brilliant insights as well as ridiculous blunders.  It is constantly evolving and changing.  Indeed, just this year, we in the United States altered how we implement daylight saving, starting it three weeks earlier in the spring and ending it one week later in the fall.  But what I’d like to focus on this month is how we divide up the planet Earth into different zones, each with its own unique time.

The origin of the longitude system (the Prime Meridian) was placed at the Royal Greenwich Observatory in England following an international conference addressing this issue in 1884.  In an ideal world, 24 time zones would each be equally spaced around the planet at 15 degree intervals in longitude.  Therefore, the relationship between the position of the Sun and local time would remain fairly close and times of sunrise and sunset would be reasonable all year long. 

Of course, in practice the boundaries of these zones zig and zag from the North Pole to the South Pole.  The reasons for these alterations from ideal time zones include those mentioned above regarding how we set our clocks.  There are also a number of time zones worldwide that differ from the standard one hour shift between neighboring zones, for example the Canadian province of Newfoundland is 30 minutes ahead of the Atlantic Time zone.

In ancient times, the concept of a time zone was unnecessary.  Wherever you were, you could always base your time on the local solar position, and if you traveled to a neighboring village or city, you would simply adjust to the new local time, as your travel time was always much greater than the difference in time between the two locations.  However, in the modern era, with the advent of faster modes of transportation such as cars, trains and airplanes, it became possible to travel to distant places at rates that were comparable to the shifting local solar time. 

For example, you can board a train in New York City and depart at 8 a.m. local solar time (LST) for Baltimore, a four hour journey.  However, your destination is located 2½ degrees west or 10 minutes behind your origin.  As a result, you arrive at 11:50 a.m. LST instead of noon (though it would be noon back in New York). 

With the growing need to standardize train schedules in the late-19th century, President Grover Cleveland established the Interstate Commerce Commission, and authorized it with the power to regulate time zone boundaries in the United States.  Its authority over time zones was transferred to the US Department of Transportation (USDOT) following the latter’s establishment in 1966.

The continental United States spans four time zones (about 60 degrees in longitude).  These are labeled the Eastern, Central, Mountain and Pacific Time zones.  The central meridians for each are located at west longitudes of 75 (Philadelphia), 90 (St. Louis), 105 (Denver) and 120 (Los Angeles) degrees.  Ideally time zones should each span 7½ degrees on either side of these central meridians to remain fairly close to local solar time.  This means that the Mountain Time zone should range from 97½ to 112½ degrees west longitude.

Boise, Idaho is located in the Mountain Time zone, but is at 116.2 degrees west longitude.  This places us 11.2 degrees west of the meridian of the Mountain Time zone, but only 3.8 degrees east of the meridian of the Pacific Time zone.  We are nearly halfway between the ideal boundary between the Mountain and Pacific Time zones and the central meridian of the Pacific Time zone.  The effect of this skewing of the time zone boundary in our area is to make both sunrise and sunset occur much later than normal.  The following table summarizes this effect for the extreme values that occur on the summer solstice (Jun 21) and winter solstice (Dec 22) for 2007.

As you can see, if the western half of Idaho and the parts of Eastern Oregon currently in the Mountain Time zone were relocated into the Pacific Time zone, these phenomena would all occur one hour earlier on our clocks.

If such a change was implemented, where would be the preferred location for the new boundary between the two time zones?  My suggestion would be to draw a line from the Utah-Nevada border straight up through central Idaho until it hits the Idaho-Montana border along the Bitteroot range, and then follow that border up to Canada.  Of course, if certain communities near this border preferred to be on one side or the other, such accommodations could certainly be implemented in any actual petition made to the USDOT.  In order to minimize disruptions, I would recommend such a move be implemented at the same time the country starts Daylight saving in a particular year.

What would be the impact of shifting to the Pacific Time zone?  One of the issues to consider here is the safety of children traveling to school in the early morning hours in December.  In the current situation, sunrise occurs in late December after 8 a.m. (MST).  A shift to the Pacific Time zone would result in sunrise occurring closer to 7 a.m., before most children have left their homes for school.

In testimony before the Energy subcommittee of the House Science Committee in May 2001, acting Deputy Assistant Secretary for Transportation Policy Linda Lawson had this to say concerning the safety issue with regards to implementation of Daylight Saving Time:

“The National Bureau of Standards concluded that morning school-age children fatalities increased in January and February 1974 when daylight saving time was being observed, compared to the same period in 1973 when daylight saving time was not observed. No comparable increase in morning fatalities, however, was found for the March and April period. While the increase was statistically significant, the National Bureau of Standards judged it impossible to attribute it to daylight saving time or to some other factor (such as weather) or combination of factors. Because of the Bureau’s findings, the Department subsequently took the position that daylight saving time in January or February might possibly increase school age fatalities in the morning.”

In a similar fashion, having western Idaho located in the Mountain Time zone may also contribute to a statistical increase in these fatalities, regardless of the implementation of daylight saving time. 

There are, of course, many other issues to consider, not least of which being the economic impact of shifting time zones.  There would be a greater need for businesses to use artificial lighting when they are open after dark.

What would be required to enact such a shift?  Well, the state would need to submit a petition to the USDOT explaining why a shift in the boundary is desired.  The legal standard involved in decisions to change a time zone boundary is the “convenience of commerce.” Indiana is in the process of seeking modifications to the boundary between Eastern and Central time zones.  Proponents are using this standard to support their petition.  Perhaps if the concerns regarding late sunrises in winter are raised, residents of western Idaho may well choose to pursue a similar course of action and petition the US DOT for a boundary shift.  Certainly, we amateur astronomers would welcome the earlier times of sunset all year long.
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For those who regularly take the opportunity to view the planets in the night sky, Venus, Mars, Jupiter and Saturn have doubtless been observed on many occasions.  However, tiny Mercury is the one classic planet in our solar system that eludes most casual observers.  This is because of its relative proximity to our Sun.  It never strays more than about 28.3 degrees from the Sun.  When the ecliptic plane makes a shallow angle with the horizon it is even more difficult to observe.  Under the best of circumstances it sets less than two hours after or rises less than two hours before the Sun.  Only if you know when and where to look are you likely to catch its brief apparitions.

Fortunately, in late May and early June, we are going to have such an opportunity in the evening sky.  A steeply inclined ecliptic plane results in a much higher altitude for the elusive planet above the western horizon.  Look for it shortly after sunset, during the fading twilight.  It will be located below and to the right of brilliant Venus, in the lower part of the constellation Gemini.  If you are unsure of which object is the planet, just draw an imaginary line between Venus and the point on the horizon where the Sun sets.  Mercury should be the brightest object visible along that line.  If you then continue that line up and to the left of Venus, the next bright object you will encounter is the planet Saturn.  The three planets all lie along this line because it represents the ecliptic plane of our solar system, where most planetary bodies orbit.

Make sure to observe the planet early in the month, because by the middle of June it will fade into sunset.  By the end of June, Mercury will have passed between the Earth and Sun and be heading towards its next morning apparition in late July.  After that, we won’t see it again until the end of September.  Because of the much shallower angle of the ecliptic at that time, the September apparition will be much less visible than the current one.

Venus and Saturn both continue to dominate the western sky after dark, but a newcomer will be vying for that position this month in the southeastern sky.  Jupiter will rise around 9:30 p.m. at the start of the month.  By the end of the month, Jupiter will be above the horizon all night long and will be the predominant object in the night sky for most of the remainder of the year.

As for constellations in June, look upwards at midnight for mighty Hercules.  Its most recognizable feature is the “keystone,” four moderately bright stars in a trapezoidal shape, separated by about 10-12 full moon lengths along each side of the figure.  If you focus on the two stars on the western side of the keystone, and gaze about 1/3 of the way from the star at the northwest corner towards the star at the southwest corner, you may discern a faint fuzzball of light.  This is easier to accomplish under dark skies or with some optical aid like binoculars or a telescope.  This object is known as the Great Globular Cluster in Hercules, and was the 13th object in Charles Messier’s list of objects that aren’t comets (M13).  It is one of the more visually spectacular objects on that list, superseded perhaps only by the Orion Nebula (M42) and the Andromeda Galaxy (M31).

Globular clusters are ancient spheroidal accumulations of stars.  They are believed to be amongst the first objects that formed when the universe was still in its infancy.  The stars that remain are all vastly older than our Sun.  These clusters encompass several hundred thousand stars in a volume only a few dozen light years in radius.  When viewed through a telescope, they look like a collection of bees swarming around their nest.  Individual stars are easily observed in the outer parts of the cluster, while the core contains the collective light of over 100,000 stars in a cluster like M13.

Next month, I’ll focus on the most prominent summertime asterism and its three points of reference.

What’s happening in astronomy around the intermountain west in June?  Here in Boise, the BAS will hold their monthly membership meeting on Friday, June 8 in Classroom B of the Discovery Center of Idaho on Myrtle Street.  We will have a presentation by our Vice-President, Randy Holst, who will discuss some of the details involved in properly aligning your telescope to enjoy a night of observing under the stars.

Over the weekend of 15-17 June, a number of BAS members will be attending a public star party at the Sugarloaf campground at Lake Cascade State Park.  We will have telescopes set up for viewing the Sun as well as a multitude of objects after dark.  If you happen to be in the Cascade, Idaho area that weekend, make it a point to come join us for what should be spectacular views.

Anyone living in the Palouse region of the Idaho panhandle and Eastern Washington may want to check out the star party on Saturday, June 16 at 9:30 p.m. (PDT) at Jewett Observatory on the campus of Washington State University in Pullman.  They house a 12” Alvin Clark refractor that is ideally suited for viewing the planets visible this month.  The Palouse Astronomical Society will also host a star party on Saturday, June 23 at Virgil Philips Farm Park, located about 5 miles north of Moscow, Idaho, starting shortly after sunset.

Throughout the summer months, the observatory at Bruneau Dunes State Park, southeast of Mountain Home, Idaho, hosts weekend open houses for the public.  A multimedia program prior to observing is available for $3/adult and children over six.  The program begins at dusk.  For more info call (208)366-7919.

Elsewhere across the intermountain west, the Northern Colorado Astronomical Society will hold their monthly meeting on Thursday, June 7 at 7:30 p.m. in the Discovery Center in Fort Collins, Colorado.  There will be a presentation on “Solar Eclipses,” at this meeting.  They also have public observing sessions scheduled on Friday, June 15 and Friday, June 22 starting at dusk at Beaver Meadows in Rocky Mountain NP, about an 80 minute drive from Fort Collins.

I encourage officers and members of other astronomy clubs throughout the west to me about their club’s activities so that I can report them here and encourage greater participation from your local community in your organization.

Update:

I just received my latest copy of the Reflector magazine from the Astronomical League.  In it are listed several public star parties taking place this month in our region, so I will provide that information here.  The first event is the Grand Canyon Star Party, taking place from June 9-16.  The 7th annual Bryce Canyon Astronomy Festival takes place from June 13-16.  For our readers in the Centennial State, the Rocky Mountain Star Stare will be that same weekend, from June 14-17.  Lastly, Desert Starlight in the Land of Enchantment at Brantley Lake State Park takes place from June 15-16.

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