Saturday: “Excuse me, do you have the time?”
“No, but the Big Dipper does.”
You can use the orientation of the Big Dipper to tell time
with a precision of about 15-30 minutes. First, find the two stars at the far
end of the Big Dipper cup, the stars that do not touch the handle. Draw an
imaginary line segment starting at the North Star and passing through the two
Big Dipper cup stars. Now, draw a big circle around the North Star. Your circle
is a 24-hour clock. Number the circle from 0 hours at the top, counterclockwise
to 12 hours at the bottom of the circle, and back up to 24 hours at the top. (O
hours and 24 hours are the same on this clock because the day is 24 hours
long.) The hour number on the big circle closest to where your imaginary line
intersects this circle is called your raw time. Due to the location of the Big
Dipper compared to the rest of the stars, the time nearest the intersection
(the raw time) is correct for March 6. For any other night, subtract two times
the number of months the current date is after March 6 from the raw time. For
example, let’s say the imaginary line between the North Star and the Dipper
stars is pointed to the right. That means the raw time is 18 hours or 6 p.m. If
you made this observation tonight, which is six months after March 6, you would
subtract two times six or 12 hours from the raw time. Don’t forget to convert
for daylight savings time if needed. If you prefer a more visual tool, and a
fun project to do with your kids, there is a simple “star clock” template and
instructions at https://skyandtelescope.org/observing/make-a-star-clock/.
Use this paper star clock whenever your watch is broken. The Big Dipper is in
the northwestern sky at 9:00 p.m. tonight.
Sunday: Mars is about a half a fist above the western
horizon at 8:30 p.m. Saturn is rising in the east at this time. By 9:30 p.m., Saturn
is one fist above the eastern horizon.
Monday: Labor Day was the brainchild of labor unions and is
dedicated to American workers. The first Labor Day was celebrated in 1882. The
Greek mythical hero Hercules probably wished there was a Labor Day to
commemorate his work. As punishment for killing his family while he was
temporarily insane, he had to perform twelve nearly impossible tasks such as
killing monsters or stealing things from deities. Hmmm. Maybe we shouldn’t
commemorate his labors. But we can enjoy his constellation. The keystone asterism
representing the body of Hercules is six fists above the western horizon at
10:00 p.m. For more information about the Labors of Hercules, go to http://goo.gl/ozVF5.
Tuesday: Had the script been written a little differently
for a well-known Robin Williams movie, we might have heard Mr. Williams shout,
“Goooood Morning Orion the hunter.” Orion is typically thought of as a winter
constellation. But it makes its first appearance in the early morning summer
sky. The lowest corner of Orion’s body, represented by the star Saiph
(pronounced “safe”), rises at 2:45 a.m. By 5:30 a.m., Orion’s belt is three
fists above the southeastern horizon.
Wednesday: School starts this week, so it is time for a
little geometry review. A square is a regular quadrilateral. This means it has
four equal sides, four equal angles, and wears old fashioned clothing. Go
outside at 9:30 p.m. tonight with a notebook in hand to sketch one. The Great
Square of Pegasus is balancing on its corner about two fists above the eastern
horizon. The top corner of the square is two fists above the bottom corner. The
other two corners are to the left and right of the line segment connecting the
top and bottom corners.
Thursday: Jupiter, Venus, and Mercury make a line in the
early morning sky. At 5:45 a.m., Jupiter is four fists above the eastern
horizon. Venus, the brightest of the three, is two fists above the eastern
horizon. Mercury is right above the east-northeastern horizon.
Friday: Geometry review, part 2. Go outside at 9:30 p.m.
tonight with a notebook in hand. (Good teaching involves a little repetition.)
A triangle is a polygon with three corners and three line segments as sides. A
good example is the Summer Triangle made up of the bright stars Vega, Deneb,
and Altair. Altair is five fists above the southern horizon. Vega, the
brightest star in the triangle, is seven and a half fists above the
southwestern horizon. Deneb is a little bit east of straight overhead.
The positional information in this column about stars and
planets is typically accurate for the entire week. For up-to-date information
about the night sky, go to https://nightsky.jpl.nasa.gov/planner.cfm.
All times are Pacific Time unless noted.
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