Magnitude discrepancy help!

[StuTodd]

I produce the local astronomical society monthly newsletter and I have a nice section on comets with a visible magnitude of 12 or less (purely a plucked number).
To see what to look up in CdC, I use http://www.aerith.net/comet/future-s.html and http://cometchasing.skyhound.com/ which produce the correct comets at the correct time. To produce a nice chart, I use a simulated plot in CdC after downloading a fresh ephemeris data set from the MPC.

Now there is often a fairly substantial (3-5 magnitude difference) between the two magnitude sources (websites and MPC).

My question is...which one would be more accurate?

I assume the MPC download in CdC?? I hate giving the wrong info out and I have traditionally leaned towards the MPC.

And out of interest, do the MPC rely on amateur observational data or do the pros submit to it too?

Stu

MPC = Minor Planet Centre and CdC = Cartes du Ciel..but you knew that

[Atmos (Colin)]

I’d be going more from the MPC personally because of the work they do in conjunction with professionals.

[StuTodd]

My thought too Colin but I wonder how the dedicated websites get it so wrong when the MPC data is there..? I'll stick to MPC data.

I assume the MPC download into CdC is current for magnitude? The path plot is so one would assume the mag is too.

[Atmos (Colin)]

Vast magnitude differences can come from the various filters being used.