angled Sunset...and why!

Event Date: December 22nd

Time: 5:00 PM

Brief

   Now with the winter solstice behind us, and the Sun already having reached its earliest date of setting a little over two weeks ago, our early evenings are starting to seem much brighter.  Although the Sun only sets a few minutes later than it did than it did on the earliest day (Dec 5th as seen from this latitude), our star spends a little more time just below the horizon this evening, than it did then.  To further show this, I will keep the horizon line in the image, yet take away the landscaping.  Also, the celestial grid shows, which traces out the Sun's local path each day, *disregarding extra declination change near the dates of the equinoxes.  In comparison, the ecliptic traces out the Sun's celestial path.

The first image shows a zoom-out, looking directly southwest; the Sun sets a little more west than this azimuth, yet that doesn't matter for the topic at hand.  

Detailed

   Look at the horizon indicated with a white line, and the angle that the celestial gridlines make with it.  Examining closely, the acute [less than 90º] angles that the lines make with the horizon, are different in measurement.  As the Sun moved from the western azimuth setting (September equinox) to the solstice, the angle that it set reflected these lines', angles, setting more gradually each day.  It is a result of this, that while the time of Sunset was nearly the same between late November and a few days after the earliest one, the Sun set more gradually; the lines indicate this anyway and therefore, we had slightly more intensity to civil twilight each evening very shortly after it set.  Civil twilight itself hardly changed in duration however, and the same for nautical and astronomical. 

   The second image is a zoom-in with a field of 20, to show the gridline angles more closely, perhaps revealing the difference as well.  Can you see the difference?  

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

Does this now explain that along with the earliest Sunset happening before the December solstice, why our evening sky seems brighter during first hour post-Sunset between the earliest day and Christmas?  In the second image, I raised the Sun to the top of the image intentionally, to show that the further south the Sun moves, the faster the gridlines move it further south of the horizon.  

   After the holidays, the Sun starts to slowly rise later more seconds apart each day, and then eventually over a minute later near the time of the equinox.