Hi Bill and Guide users.

Thanks for the tip on getting correct magnitudes for Comet P/Holmes. Your
suggestiion got me thinking of a way to get the comet symbol to match my
images of the fuzz ball. By setting the H value to zero I get a circle for
the comet on my ccd frame display in the guide map that nearly matches the
size of the comet cloud on my CCD images.

Bob Elliott
MPC 762
Lake Leelanau


At 19:32 2007-11-04 -0600, Bill J Gray wrote:

>Hi Thomas,
>
> Best I can suggest, at least right now, is to use the following
>logic: this object is in the ballpark of mag 2 now, fifteen magnitudes
>brighter than what you'd get with the current H value. So change H
>from 10 to -5, and you'll get a passably correct current magnitude.
>
> Which is about all we can hope for. We don't know what this object
>will do in the future, so the best we can do is to "brute force" the
>magnitude to something close to its current value.
>
> So. Use Extras... Edit Comet Data, and select P/Holmes. You'll
>see the H value given in the resulting dialog. Change it to -5, and
>click OK.
>
> The comet will then appear _much_ larger in Guide, with a five-degree
>tail.
>
> It occurred to me that H=-5 is a _very_ bright comet. (It means that,
>were the object one AU from the Sun and you were standing on the Sun,
>the comet would be a mag -5 object... sort of a measure of how intrinsically
>bright the object is, with the effects of distance from the sun and observer
>removed.) The closest in recent times was Hale-Bopp, with H=-2, making
>this object (at least briefly) three magnitudes bigger and brighter than
>Hale-Bopp. Gives you an idea as to just how enormous an outburst this is.
>
>-- Bill
>
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