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Chasing Comet ISON

Last updated January 2, 2013

Comet C/2012 S1 (ISON) was the subject of a great deal of attention after its discovery in September 2012. At that time it was still far from the sun on its journey toward the inner solar system. Comets are inherently unpredictable, but it appeared that this comet had the potential of becoming very bright, perhaps easily seen by the naked eye. As a result, it received attention in the media and became rather famous. Aware of the possibility that it might not survive and/or put on the big show people had hoped for in December, many amateur astronomers successfully observed it with their telescopes prior to perihelion in November. Coincidentally, there were several other bright comets that were also visible in small telescopes during those early mornings in November, and one legacy of ISON is that the interest it generated led many more people to observe these pre-dawn comets.

Archived Reports

As of December 10: the early observations of the ISON remnant have yet to be reproduced, either visually or via imaging. It may have further dispersed and faded in the intervening days. Imaging ISON is very difficult at this stage, due to the need for a wide field of view coupled with bright twilight. Attempts to image a surviving nucleus have so far shown nothing.

As of December 7: the remnant of comet ISON has been recovered visually. It is faint and diffuse -- not at all the comet that many had hoped for. It is interesting to observe nonetheless. As it rises higher above the horizon in the coming days it will also likely continue to fade. Currently it should be possible to observe the remnant in just about any telescope, but the conditions must be excellent. A clear horizon and very little light pollution are necessary to see it.  The conditions are more important than aperture, and It may be difficult to spot even in larger telescope due to its diffuse appearance. Low magnifications are recommended.  

J. J. Gonzalez reports the following observation on December 7:
The comet's remnant visually shows a near-elliptical area with a slightly higher degree of condensation and 10' of major axis, with geometric center located approximately at R.A.=16h11m.8, Decl.=-1o45'.0, about 20' separation in declination respect to the pre-perihelion ephemeris position. Two faint tail-like structures are observable, the best defined one along 0.3-deg in p.a. 310 deg, and the other one appears shorter and directed towards p.a. 180 deg.

At Perihelion (November 28): as ISON approached  perihelion (closest approach to the sun) it unexpectedly faded, as seen in SOHO satellite imagery. It appears to have disrupted, if not completely disintegrated. Yet something of this comet did survive, although greatly diminished. 

Meanwhile, the pre-dawn still offers several bright comets. 2013 R1 (Lovejoy) is currently naked eye, although binoculars offer the best view. 2012 X1 (LINEAR) is visible in binoculars, and 2013 V3 (Nevski) is visible in small telescopes. Two comets are available in the evening this month in 6-inch or larger telescopes. See the Comet Chasing page for charts and more information about these comets. 

I will continue to update this page regularly as more information comes in.

FINDER CHART (December 5-15)  

Seeing a comet visually is more difficult than the pretty pictures make it appear. Standing next to the photographer above, few people would have noticed comet PANSTARRS last spring and binoculars were required for most to see it at all. The story linked below details our experience using SkyTools to successfully plan for PANSTARRS observations.

How Software Can Help You Observe Comets


Cometography C/2012 S1 (ISON)