Summer Triangle stars' positioning

Event Date: January 12th

Time: 6:30 AM/PM

Brief

   At the beginning of the month, I mentioned that the Summer Triangle was just barely above the horizon in its entirety; least-northern star Altair being the only one to be too close to the horizon to see easily.  That has changed, and now all three stars can be seen with an unobstructed horizon.  If skies are clear enough, Altair can be seen above the horizon, while Vega and Deneb are already easily visible, high enough.  What is interesting about the Triangle this week, is that 12 hours before and after the morning viewing, it can be seen at about the same altitude of sky...or Altair itself, anyway.  The position of each star relative to each other seems different, yet we can still see all three of them.  

Let's take a look at an image for both parts of the day to see this: AM followed by PM, 6:30 each time.

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

Detailed

  Once again, while looking at both of these images, Altair is about the same altitude in each, which is important to see the entire triangle.  Remember however, that the stars' rising and setting is not symmetrical to the meridian; these stars make different size circles around the north celestial pole and therefore, always the same separation from that coordinate in the sky: 90º declination.  

    From mid-northern latitudes, Altair rises well after Vega and Deneb, and sets not long before Vega.  Why?  It is only 9º N vs Vega and Deneb's 38º and 45º declinations respectively.  This is a big difference in the number of hours that each star is above the horizon as seen from these latitudes.  For example, at 38º N, being approximately that of these images, Vega spends 17.3 hours above the horizon, Deneb spends 19.1 hours, and Altair spends just slightly over 13 hours.

The higher the northern latitude that one views from, the closer Deneb and Vega get to being circumpolar, while it takes a trip to 81º north to see Altair go circumpolar, being declination 8.9º.  If you prepare accordingly and don't mind watching the star for 24 hours with little or no warmth that close to the pole, go for it-- not many others make such an effort!  Then again, you can use the more comfortable--even if less conventional--way of doing so, by buying a version of astronomy software such as what you see samples of above!  That, or go online, time-bend the clock of applicable, and watch the star move along/above the horizon in a matter of seconds!  After thinking about it, seeing it live would probably be much more adventurous and real-like!