Re: [guide-user] comet ISON

Bill Gray Feb 16, 2013

On 02/16/2013 06:52 PM, jimborm@... wrote:
> I too agree with your coordinates, but I wonder if the comet is bright
> enough to show in a 60" image. GUIDE shows me that its magnitude should be
> about 15.2 (although I don't remember where I got my mag data from).

Comet mags are bound to be somewhat iffy. They're usually based on an
effort to fit the entire observed arc, which may mean it'll fit well
in one place but not another, especially if outbursts are involved.
(If the comet suddenly brightens by six magnitudes, for example, you
can't really tweak one set of magnitude parameters to show both "before"
and "after" magnitudes correctly.)

I went to the MPC Database Search at

and in the first edit box, for "Data about an object", I entered ISON
and clicked on "Show". That got me several orbits, and further down,
it said there were 2078 observations available and that they were available
for download.

Doing so and scrolling down to the bottom, I saw several dozen observations
made on 11 February, with magnitudes of 16.0 to 17.2. (With a few outliers
brighter or fainter than this.) So it would appear to be fainter than
predicted, at least right now.

-- Bill