Archive for August 12, 2021

08/12/2021 – Ephemeris – It’s not too late to see the Perseids

August 12, 2021 Comments off

This is Ephemeris for Thursday, August 12th. Today the Sun will be up for 14 hours and 10 minutes, setting at 8:52, and it will rise tomorrow at 6:43. The Moon, 3 days before first quarter, will set at 11:13 this evening.

It’s not too late to see the Perseid meteors. The projected peak of the shower is expected to be between 3 and 6 this afternoon. So the meteor shower should still be quite active. It has been my experience that the numbers of meteors decline more rapidly than they increase before the peak. NASA can determine their orbits using all sky cameras placed at different locations to get their paths by triangulation. The cameras have shutters the interrupt the meteor track at a specific interval, which allow them to determine the meteor’s speed and are able to calculate the particle’s orbit of the Sun. An animation of these orbital tracks can be found on the International Meteor Organization website

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.


I’ve been talking about the Perseid meteor shower all week, so far. Click on the calendar dates to the upper right to review those posts.

Perseid outburst in 2009

A Perseid outburst from 2009. Credit NASA/JPL via Phil Plait’s Bad Astronomy.

Perseid fireballs in NASA all sky camera

Perseid fireballs in one of NASA’s all sky cameras during the morning hours of August 13, 2017. This is a long time exposure. The bright swath in the image is the Moon that morning. Since it is a time exposure, the radiant is also moving with the earth’s rotation, so the meteors only seem to come from the northeastern sky. North is at the top, and East is to the left. Credit NASA.