Catch a comet in September's evening sky

COMET WATCHING The comet Christensen was discovered in 2006 by Eric Christensen, and can be viewed in the September sky. Photo by the author

Amateur astronomers and sky enthusiasts can watch comet Christensen in the evening skies of September. Comets are icy bodies, orbiting in the solar system, and partially vapourise when they near the sun, developing a cloud of dust and gas and, normally, one or more tails.

Some of them are large enough to be detected in the outer solar system. The smaller comets may be as insubstantial as a snowball and melt away into fragments as they come closer to the sun. Professional observatories rarely have time to devote to scan skies in search of new celestial objects, so amateur astronomers using simple equipment often discover comets.  

In the evening sky
C/2006 W3 Christensen will be clearly visible in the evening sky to Northern Hemisphere observers. You can watch it with the aid of small binoculars in the constellation Vulpecula in the higher horizon of the eastern sky. The comet was discovered on November 18, 2006 by Eric Christensen during the course of the Catalina sky survey going on in Arizona; this is his 15th comet discovery, out of a total of 19. Christensen’s comet is a very bright one, but because of its large perihelion distance, it  won’t be a bright object in our skies. It is currently located in the northern circumpolar skies (declination +64 degrees) in the constellation Camelopardalis, a few degrees south of the star Alpha Camelopardali.
When a new comet is discovered, or a periodic comet recovered, it is given a designation consisting of the year followed by an upper-case letter indicating the half-month of discovery in that year. The prefix P/ is added for short-period comets and C/ for long-period comets. Periodic comets that have disappeared or been destroyed are prefixed by D/. New comets are named after their discoverers, no more than three names being permitted when there are several independent discoverers. A few comets have been named after individuals who calculated their orbits (e.g. Halley and Encke) or after observatories or satellites, where discovery was essentially through the efforts of a team.

Comet Christensen can be seen in the high eastern sky at a magnitude of 8 (less the value of magnitude, greater the brightness). The most advisable place to watch this comet is a hilly area or a remote place free from city lights. But, it is impossible to see a comet under moonlight. Comet Christensen is usually seen at 11:10 pm. But the best time to witness this periodic comet is around 11:50 pm. Even with the help of small telescopes and binoculars, the comet can be spotted easily.                    
The traditional ways in which comets were discovered by amateur astronomers may be things of the past. With an increasing number of professional all-sky survey programmes, many specifically designed to spot moving or changing objects, may mean that the prospects for amateur astronomers of discovering comets visually may come down.
In the near future, professional surveys are likely to cover most of the dark sky, perhaps down to a magnitude of 24.

Photographing comets
The photography of comets with film still retains importance after more than a century of development, especially for wide-angle imaging. Simple astrophotography methods and advanced techniques will both yield beautiful images for causal photographers and experienced astronomers.
In the simplest approach to shooting comet photographs, a tripod is used to hold and aim the camera.
More elaborate efforts use an equatorial mounting, which counteracts the rotation of earth, following the comet as it moves across the sky with the earth’s diurnal rotation.
Such a mount can even be used to track the comet as it moves with respect to the stars in the background. Amateur astronomy has taken great advantage from the introduction of modern digital imaging techniques, and their application to cometary science makes no exception. Thanks to the characteristics of CCDs (charged coupled devices), interesting images of comets are routinely obtained, even under light-polluted suburban skies. The reflecting telescope with 4-inch or 6-inch reflector will do to witness this comet.

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