Both values represent elements of the comet's intristic magnitude of
brightness of the comet.
Starting with "6.0" in your example, is listed in Guide as the "Slope
parameter" or angle at which the comet is illuminated by the sun.
The "8.0" is listed in Guide as "Absolute magnitude" or the comet's
magnitude at 1AU as seen from the sum.

These numbers are very tricky to play with and authoratative info is
necessary to get accurate results.

I hope this sheds a little light on the problem.

Mark S Deprest

--- In guide-user@yahoogroups.com, "Scott Kranz" <s.kranz1@...> wrote:
>
> This is a basic line from the comet data file that GUIDE uses:
>
> P/Faye (4P) 15.4815 11 2006
> 0.0 1.667245 0.566586 9.0317 205.0300 199.3073
> 2000.0 8.0 6.0 MPC 48384
>
> Can anyone tell me what the 2nd (value 6.0 in above example) and 3rd
> (value 8.0 in above example) from last fields are?
>
> When you get GENERATED files from the MPC they both are returned as a
> value of 0.0. GUIDE recognizes that as having a magnitude 99.0!
>
> Thanks!!!!!
>
> -Scott K.
>