When is the best time to observe Caldwell 22?

Caldwell 22 is best observed from August through October, with peak visibility during September when it transits around midnight in the Northern Hemisphere.

Where is Caldwell 22 located in the sky?

Caldwell 22 lies in the constellation Andromeda at right ascension 23h 26m and declination +42° 32′.

What telescope do I need to see Caldwell 22?

At magnitude 8.3, Caldwell 22 is within reach of a 3-inch (80 mm) telescope from a moderate-Bortle site.

Caldwell 22 — Planetary Nebula in Andromeda

NGC 7662

Planetary Nebula Excellent (70/100)

Magnitude 8.3^m PlanetaryNebula Andromeda Visible

Credit: Judy Schmidt. License: CC BY 2.0. (Wikimedia Commons)

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About Blue Snowball

Description

The Blue Snowball (NGC 7662) is a planetary nebula in Andromeda, about 5,600 light-years away. It has a distinctive blue-green color and a complex multi-shell structure visible in photographs, with a bright inner ring spanning about 12 arcseconds.

Observing Tips

Easy to find and satisfying in small telescopes. A 4-inch scope shows a bright blue-green disk at 100x. Higher power (200x+) may reveal the annular structure. An OIII filter enhances the view. Best in autumn evenings.

History

Discovered by William Herschel on October 6, 1784. It earned its name from its vivid blue color, unusual among planetary nebulae which more commonly appear green from OIII emission.

Fun Facts

The Blue Snowball has multiple concentric shells from successive mass-loss episodes. Its central star has a temperature of about 75,000 K and a luminosity 2,000 times that of the Sun.