The Total Lunar Eclipse of Sunday, January 20<sup>th</sup>, 2019

The Total Lunar Eclipse of
Sunday, May 26th, 2021

The first total lunar eclipse visible in Idaho since January, 2019 will be a very shallow total eclipse, with the moon spending only 15 minutes completely in Earth's full shadow.

May 26, 2021 lunar eclipse phases

Adapted from a diagram by NASA.  Note that, although the moon's orbital motion will cause it to move to the upper left (east) relative to Earth's shadow, it (and the shadow) will be moving to the lower right (toward the western horizon) due to Earth's rotation.  Thus, for observers in Idaho, the moon will be moving lower in the sky relative to the local horizon throughout the eclipse.

Eclipse timeline (all times listed are in Mountain Daylight Time (GMT-6 hrs.), and rise/set/twilight times are given for Twin Falls, Idaho, USA):

  • 2:48 AM — First penumbral contact (P1).   The left edge of the moon begins to enter Earth's penumbral (partial) shadow.  The subtle decrease in illumination of the moon will not be noticeable to the eye.
  • 3:30 AM — Centennial Observatory opens for public telescope viewing, weather permitting.  Please dress warmly!  By this time, the left side of the moon will appear subtly darkened.
  • 3:45 AM — First umbral contact (U1).  The moon begins to enter Earth' umbral (full) shadow.  A small, dark "bite" begins to grow ever larger from the moon's lower left edge.
  • 4:00 AM — Start of morning astronomical twilight  The sun is 18° below the horizon, bringing the first hint of pre-dawn glow to the northeastern horizon.
  • 4:20 AM — Moon too low to view with the 24” telescope.  Viewing from this point on will be with small telescopes outside.
  • 5:11 AM — Total phase begins (U2) (second umbral contact).  The moon is completely immersed in Earth's umbra, appearing dark red-orange, orange-brown, or darker depending on global atmospheric conditions, darkest at the lower left and brightest at the upper right.
  • 5:20 AM — Greatest eclipse.  The moon reaches its maximum excursion into the umbral shadow, appearing at its darkest for this eclipse.  For this particular eclipse, the moon passes well north of the center of Earth's full (umbral) shadow, so it will probably not get extremely dark, with the upper right edge noticeably less dark than the lower left, which is deepest into the shadow.
  • 5:26 AM — Total phase ends (U3) (third umbral contact).  The moon begins to emerge from Earth's umbra, with a growing, bright sliver appearing at upper right of the lunar disk.
  • 5:30 AM — Observatory closes.  Partial phases continue until after moonset.
  • 6:06 AM — Sunrise.  Roughly half of the partially-set Moon has emerged from umbral shadow.
  • 6:15 AM — Moonset.  The moon sets in Southern Idaho while less than half-way out of umbral shadow, ninety-four minutes before the end of the final partial phase (U4), at 6:52 AM.