A Spring Rosette and the Ghost of Jupiter

An old favorite of mine is the Rosette Nebula (NGC 2237–39) to the east of Orion in the stellar wilderness we call Monoceros. Without a filter only a tiny glimmer of light is visible, but with an ultrahigh-contrast (UHC) filter the nebula bursts forth in spectacular fashion. I know of no other object in the sky where flicking a filter back and forth in front of a a naked eye produces such a wonderful effect. Indeed, about 1983 both Brian Skiff at Flagstaff, Arizona, and I independently viewed the Rosette with the naked eye and a nebula filter.

The Rosette is one of the few deep-sky objects better seen with a telescope's finder than with the main instrument. With large binoculars and good observing conditions, the Rosette may appear as a formless aura of soft light encircling a cluster. But equipped with a proper filter, just about any telescope will show it.

There is a fine planetary nebula in Hydra, NGC 3242. It is located about 2° south and slightly west of the 4th-magnitude star Mu (μ) Hydrae. It's sometimes called the Ghost of Jupiter because it's similar in size and color to the planet Jupiter. The total light of NGC 3242 roughly equals that of an 8th-magnitude star. With a disk only 0.5' in diameter, the surface brightness of this planetary is quite high, averaging about 10 times greater than the Ring Nebula in Lyra. I looked at it with my 5-inch Apogee telescope and a 20x eyepiece. It appeared slightly oval but without the pointed ends so prominent in photographs of the object. I also examined NGC 3242 with a Lumicon UHC nebula filter. The results were impressive.