DSO of the Month
Caldwell 22
AKA: Blue Snowball Nebula; NGC 7662.
Position: 23 hr 25.9 min 42 deg 32 min 6 sec
Due south at 22:48 (BST) on 15 October
Image of Caldwell 22 by HAS Member Martin Gill. Used with permission.
We return to another planetary nebula, this time in the constellation of Andromeda, namely Caldwell 22 better known as the Blue Snowball. As is often the case with planetary nebulae, it is fairly faint at a magnitude of 8.6 and has a diameter of 37 arc seconds, hence roughly the same size as Jupiter. Nonetheless it can usually be easily seen in a small telescope with a relatively high magnification. A telescope of at least 125 mm in aperture should reveal a tiny bluish disc. It was discovered by William Herschel in 1784 and it is one of those planetary nebulae whose appearance fits the term planetary, although they have nothing to do with planets. It seems that the name Blue Snowball was coined (perhaps unwittingly) by the amateur astronomer Ronald Morales in 1986 when he remarked in ”The Amateur Astronomer's Catalog of 500 Deep-sky Objects” that it looked like a blue snowball.
It is not easy to find, but it is roughly half-way between Alpha Cassiopeiae (Shedir) and Beta Pegasi (Scheat) under the unremarkable constellation of Lacerta. It is one of those objects where you really need go-to as it is not easy to spot in a finderscope.
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