[BAA Comets] Comet magnitudes

[Nick James]

Roger,

As Jonathan says they are using different magnitude parameters:

JPL Horizons has M1 = 12.2, K1 = 11.0
MPC have 9.8 and 15.0

Both using:

T-mag =  M1 + 5*log10(delta) + k1*log10(r)

Yoshida has M1 = 7.2, K1 = 20 with r delayed by 30d. This is closer to 
the running COBS estimate.

It's a comet, so you can take your pick! None of these simple models fit 
the observations very well.

Nick.


On 26/06/2017 14:32, Roger Dymock wrote:
> For comet 71P/Clark on 2017 June 24 the MPC Minor Planet Ephemeris Service
> gives a value for m1 of 11.7. The JPL Horizons website returns 13.3 for the
> same input. Any ideas as to why they should be different ?
> 
>   
> 
> Regards
> 
> Roger Dymock
> 
> www.britastro.org/projectalcock <http://www.britastro.org/projectalcock>
> 
> Skype; rogerdymock67
> 
> Tel; 023 92647986
> 
>   
> 
> _______________________________________________
> Comets-disc mailing list
> Comets-disc at lists.britastro.org
> http://lists.britastro.org/mailman/listinfo/comets-disc
>