Big Dipper pointer stars: same altitude

Event Date: March 11th

Time: 8:31(.25) PM

Brief

   I have shown the Big Dipper's "pointer stars" Dubhe and Merak several times, leading almost directly to the north celestial pole; even moreso to Polaris, which as a reminder, is 40 arc-minutes from the pole.  This evening, I will get a little fancier with the dipper stars.  If they can point together towards another star, how about pointing towards... each other??  Okay, that may sound weird, yet what I am referring to, is their altitude.  With an altitude/azimuth telescope, a viewer--for the fun of it--can slew from one star to the other at the time above.  At about 5.4º apart, they are just over 44º high.  Notice that at our used-latitude of just under 38º, this is a little over 6º further north than the celestial pole.  Therefore, it verifies--by number--how far the stars point away from the pole and namesake star.

   Here is the Dipper and stars.  I chose an azimuth almost directly between them, to show that the part of the stick figure that connects them is almost perfectly straight.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

   We have seen the Dipper with these stars at this position in the sky at later hours of the evening and early hours of the morning over the last several months, heading backwards in time.  Since the asterism is circumpolar to us, it depends what time of year it is for us to see it most frequently in the northeast this way, seemingly standing on its handle [stars].  Other times, we see it high in the north, and looking as if it pouring out content of some sort.  Finally, when seeing it in the northwest, it looks as if it is almost resting on its cup, with the handle curving down towards towards Arcturus and then (if still above the horizon at the time) Spica.  Of course, I am talking about the spring arc asterism, which beginning next month, spends the entire evening above the horizon.  I will review the arc in after the equinox.  Until that time, enjoy the shape and positioning of the Dipper.  Watch how slowly it moves during the 23 hours, 56 minute (sidereal) day.  To go 360º around the pole, that means about an hour to go 15º.  This may not mean much to us, except that when watching it, we hardly notice movement until several minutes later.  Of course, the Dipper and all other stars don't move that fast in that sky: we are.  Thank goodness for tracking telescopes to (sarcastically) eliminate such confusion!