Scheduled time for Public Observing: 9pm – 11pm

Solar System Objects:

The Moon: will be 33° high in the SE at 10pm, and 96% illuminated (Full phase, 13 days old).

Image (c) Virtual Moon Atlas /

Planets: at 9pm, Saturn will be 19° high in the SW, just below the 20° limit for the 20″ refractor, but there may be telescopes set up outside for viewing. Mars will be 24° up in the South, and 17 arc seconds in diameter, with some surface detail visible, especially the polar ice caps. Mars has been undergoing a planet-covering dust storm this summer, which now seems to be clearing to some extent. Weekly updates can be seen here. Neptune will appear near the Moon, and Uranus will be visible in a telescope at 33° altitude in the East by 11pm.

Deep-Sky Objects:

Double Stars: Located nearby the moon tonight, Zeta Aquarii is an interesting binary star. It’s components appear very close together, about 2.5 arc seconds apart, but would be resolved in the 20″ scope if the atmosphere is stable enough. The stars orbit each other with an (uncertain) period of 760 years, and are 92 light years from earth.

Red Stars: TX Piscium is a red “carbon star” also in the same area of the sky. Visually very red thru a telescope, it’s about 2x the mass of the sun, but because it has evolved into a red giant, it’s about 590x the diameter of the sun and 7,000 times brighter. It’s distance is estimated to be 900 light years.

Nebula and Star Clusters: Between the double stars Enif (Epsilon Pegasi) and Gamma Delphini is the globular star cluster M15 (shown below, courtesy Rob Gendler, also nearby is the Saturn Nebula (NGC 7009). With the moon nearly full, these objects will appear washed out by the sky brightness, but may still be visible. Special filters might help.

Man-made Objects:

International Space Station (ISS): At 8:37pm (before the official start of Public Observing) the ISS will make a pass moving from SW to NE, and will be magnitude -3.5 (a little fainter than Venus). It will disappear overhead when it enters the Earth’s shadow.

Iridium Satellites: These satellites can produce bright flares (brighter than Venus) from their antenna arrays. Any visible flares will be added closer to the observing date, as prediction accuracy improves. *Update*: Sorry, no flares are visible tonight.