SKYWATCH: September 2021
By Phillip Virden: Lake City, Colorado Amateur Astronomer, Cooperative Observer for 30+ years for National Weather Service, Dark Sky Coordinator for Lake Fork Valley Conservancy
Round Top’s aspen “stamp patch” on last year’s Autumnal Equinox
“The vibrant season,
Chroma of amber and dust.
Nature’s masterpiece. ”
Changing of the Seasons
August Weather Averages
Average high temperature was 76.0 vs 74.1 historical average.
Highest recorded temperature was 83 on August 13.
Average low temperature was 43.5 vs 43.4 historical average.
Lowest recorded temperature was 38 on August 21 and 22.
Average mean temperature was 59.75 vs 58.8 historical average.
Total precipitation was 1.47” vs 2.22” historical average.
September Weather Averages
Historical average high 68.8
Historical average low 35.8
Historical average mean temperature 52.3
Historical average precipitation 1.33”
Summer into Autumn
I love the change in seasons…summer with its wildflowers & wildlife…autumn with its theatre of color change…winter with its snow and early starry nights…spring with its hope for warmer days and the reward of aspens turning green. So why do we have the seasons? Primarily it is due to Earth’s axis which is tilted. In a year’s time, the Earth receives Sun’s most direct rays in certain locations. For instance, when our North Pole tips to the Sun, it is summer in the Northern Hemisphere and winter in the Southern Hemisphere. Six months later, the South Pole now angles to towards the Sun and its winter in the Northern Hemisphere and summer in the Southern Hemisphere. Normally, around June 20 marks the Summer Solstice and December 20 marks the Winter Solstice.
In between, we have the Vernal (spring) and Autumnal (fall) equinoxes. An equinox means the Earth’s axis is not tilted towards or away from the Sun. On the equinox, we have nearly 12 hours of daylight and 12 hours of night. This year, the autumnal equinox occurs on September 22. Enjoy the artistic change of the aspens and cottonwood along with chillier nights and the start of the first of three “Indian summers” (stretches of sunny days in September, October, and November).
The Summer Triangle
The “Summer Triangle” is an asterism made up of three stars from three different constellations – Vega in Lyra the harp, Altair in Aquila the eagle, and Deneb in Cygnus the swan.
Pegasus
Fall’s landmark asterism contains four stars of the constellation Pegasus – Alpheratz, Scheat, Markab and Algenib.
Fall Constellations
A good geometry lesson takes place this time of year. The Summer Triangle dominates the zenith in the early fall months but rising in the east is a square! The Great Square of Pegasus means it is the end of summer and the start of fall. So, it’s fun to see both a triangle and square at the same time at night. Other autumn constellations include Aquarius Aries, Pisces, Andromeda, Perseus, Cassiopeia, Cepheus, Cetus, and Lacerta. Bright stars are few in autumn but see if you can spot bright Fomalhaut in the constellation Pisces.
Lonely bright star of the autumn southern sky is Fomalhaut in the constellation of Pisces. It shines at a magnitude of 1.16 and is “only” 25 light years away.
September Sky at Night
September 2 – Venus and Spica will appear close together in the southwest at dusk.
September 3 - The thin waning crescent Moon will appear near Gemini at dawn.
September 6 - New Moon
September 12 - That’s reddish Antares near the Moon tonight.
September 15-18 – Watch for Moon passing through Saturn and Jupiter.
September 20 Bright Full Moon – Known as the Harvest Moon.
September 22 Autumnal equinox – It is officially the start of fall!
September 28 Last quarter Moon.
Weekly Summer Stargazing Programs Begin
Lake City Skies will be holding stargazing sessions this September at Windy Point. They will be from 7:30 p.m. to 9:30 p.m. MST. View all upcoming sessions here! People are asked to dim their headlights when they approach the site, wear warm clothing and bring something to sit on. Bring your telescopes, binoculars, your own star knowledge, and enthusiasm!
*Inclement weather (rain, lighting, total cloud cover) will cause for cancellation of session.
If you have a question or would like to share information or your own photo, email Phillip Virden at starmanlakecity@msn.com