SKY REPORTER: Seeking Dark Skies

Earth at Night
Credit: NASA

With summer’s official northern hemisphere conclusion September 22, cooler temperatures and less hazy skies gradually will allow clearer nighttime sky watching. Although solar system objects such as the Moon, Venus, and Jupiter are easily seen even from Manhattan, fainter planets and stars are certainly best viewed from darker sites. As a guide when planning a visit to such locales, the following references offer guidance.

Attilla Danko's Clear Sky Chart provides a wealth of astronomically useful short term weather forecasts and observing information specific to hundreds of sites throughout North America. Danko includes advisories considerably more detailed than usual media reports. Descriptions are based on data from Allan Rahill’s work at the Canadian Meteorological Centre. Charts show aspects helpful when planning observations up to about 48 hours in advance. Each chart covers a geographic area typically about ten miles in radius and includes seven rows of color coded pixels indicating conditions of cloud cover, sky transparency, seeing conditions, darkness, wind velocity, humidity, and temperature.

Another fine aspect of Danko’s CSC is a graphic based on the light pollution atlas of David Lorenz. It shows relative sky darkness over a range of several hundred miles centered the featured sites. You can click on sky locations indicated by progressively darker colors to show coordinates and maps. It’s a big help when planning observing trips.

You can also get in on the action by measuring relative darkness of astronomical viewing in your area by participating in this month’s “Globe at Night” survey. During the period September 15-24, observers in the Northern Hemisphere will be counting stars in the constellation Cygnus and reporting their results for inclusion on the project’s updated maps. Sky conditions will be rated in five levels of darkness or lack thereof: City Sky, Bright Suburban, Suburban, rural, dark sky.

The Moon

The Moon is less than 224,851 miles from Earth on September 7th, 8th, and 9th. Those nights the lunar face thereby satisfies the popular definition for being a so-called Super Moon.

In New York City Monday September 8, the Super Harvest Moon rises at 6:55 p.m., 21 minutes before sunset. As it rises, the Moon’s center to center distance from Earth is 223,072 miles. Many news reports may mention the Moon on the night of the 8^th, but remember one night before and after that date we will also see a Super Moon, looking a bit larger and more impressive than usual.   

Planets

Early Saturday morning September 20, The Moon is to the lower right of Jupiter.

Autumn arrives in the northern hemisphere at 10:29 p.m. the evening of Monday the 22. At that moment the Sun is directly above a point in the ocean 177 miles north of New Guinea’s coast.

During the last week of September Mars, known as the Red Planet and Antares, a red supergiant star, whose name means “Rival of Mars” are in apparent proximity. They’re about three degrees apart on the 27 and 28.

As twilight fades the evening of Saturday the 27, Saturn may be seen three degrees to the upper left of the Moon.

The nights of September 29 the Moon is several degrees above Mars and Antares.