February evenings: what better time to observe?
FEBRUARY'S OBJECTS Name Type Coordinates epoch 2000.0 M42 diffuse |5.sup.h~ |35.sup.m~.4 nebula -5|degrees~ 27' M41 open |6.sup.h~ |47.sup.m~.0 cluster -20|degrees~ 44' NGC 2283 galaxy |6.sup.h~ |45.sup.m~.9 -18|degrees~ 14'
In the early evening the atmosphere is turbulent with the day's accumulated solar energy radiating back into space. Stars twinkle vividly. It is at these times that I like to turn my telescope on brilliant Sirius and watch it dance in a rainbow of colors. There are shades of red, splashes of green, and a range of blue.
As the seeing settles, I'll nudge my scope 4|degrees~ to the south and check out the open star cluster M41. Covering a Moon's diameter of sky, this loose scattering of stars is visible to the naked eye. Aristotle is said to have referred to the group as a star with a tail. In my early days of observing I never noticed M41 as a naked-eye object even though it was described as such in Thomas W. Webb's 19th-century classic compendium, Celestial Objects for Common Telescopes. William H. Smyth, author of another 19th-century observing handbook, talked more about a double star within M41 than about the cluster itself. I suspect he would have been more enthusiastic had M41 been better placed above the horizon at his home in England. Indeed, last month I wrote about exploring the sky while in Mexico. At this southern latitude M41 was a grand naked-eye sight.
Considerably more challenging is the 12th-magnitude galaxy NGC 2283 about 1 1/2|degrees~ south of Sirius. It lies less than 1/4|degrees~ east of the northern star in a prominent chain of three situated about halfway between Sirius and M41. I have seen the galaxy with my 4-inch Clark refractor.
The Orion nebula is certainly one of the greatest attractions in the sky. But all too often experienced deep-sky observers only glance at this "easy" object, opting to devote their observing skills to more elusive targets. Several times I have asked for reports on the texture of the conspicuous nebulosity just south of the four bright stars forming the Trapezium. The great English observer John Herschel vividly described the nebulosity as looking like "a curdling liquid or a surface strewn with flocks of wool, or to the breaking up of a mackerel sky."
At first there was little response to my requests. Then Eric Bunn of Westford, Massachusetts, sent a delighted reply. Over the years Bunn has observed M42 with a variety of telescopes ranging from a 2.4-inch refractor to an 8-inch reflector. But he had never noticed the texture described by Herschel. After reading my comment, however, he examined the nebula with a 6-inch f/9 refractor made by Astro-Physics and immediately noticed the effect. "It is an extremely impressive sight," he writes, "especially when I saw it for the first time. I never guessed it was there. Under very steady seeing conditions I have noticed a very faint reddish tinge at the fringes of the nebulosity." Perhaps this will inspire others to look.
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|Title Annotation:||Deep-Sky Wonders; observations on the Orion constellation and nebula|
|Author:||Houston, Walter Scott|
|Publication:||Sky & Telescope|
|Date:||Feb 1, 1993|
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