September equinox

Event Date: September 22nd
Time: 7:43(.11) AM


Brief

   Happy September equinox!  For northern hemisphere viewers, we can also say "happy autumn".  It is hard to believe that this much time has passed already since my first blog-entry of my journals, featuring the March equinox.  As a result of my excess text and images there, I will keep this one much shorter. 
    As the case with the March equinox, the September one features the Sun crossing the celestial meridian and ecliptic at almost the same time...but not quite; the detailed section tells those following the images below of the zoom-out and zoom-in of the Sun and lines.  Also, as the time shows above, it crosses the ecliptic meridian at a slightly different time.

Detailed

   As I mentioned when talking about the March equinox back then, there are very few times over centuries-worth of years, that the Sun will cross the ecliptic, ecliptic meridian, and/or celestial meridian at the same time; crossing all three at the same time is beyond extremely rare, yet the spacing in between such times is very small so it isn't worth getting concerned over when calculating the equinox.  For this one, the time that it crosses the celestial meridian is 7:37(.30), and the time that it crosses the celestial equator is 7:35(.03) PM.  Once again, these differences can vary with each equinox from year to year.  When looking at the zoom-in for image two above, if we imagine precisely where the Sun's center is, the intersection of all three are close.  An even further zoom-in below, taking the Sun away, still has the image centered at the Sun's center, and we can see that all three--the meridians and celestial equator--don't all meet at one point.

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