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.
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
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.
CHART (December 5-15)
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.
Software Can Help You Observe Comets
C/2012 S1 (ISON)