Rereading my prev msg. I don't think I might have been very clear on what I was asking.

Here is an example from 878 Mildred. The upper part of this info list the absolute mag at 15.0 but the lower section (from MPCORB) shows 14.6

Why the difference in the two stated values? What is the source of this upper portion of info? I also found similar differences in absolute magnitude values being listed in the Guide 'more info' on several other randomly chosen minor planets.

======from Guide 'more info' page=====

(878) Mildred mag 19.8
Right ascension: 18h12.693359m
Declination: -21 43.5115'
Mean position at current epoch:
Right ascension: 18h13.301356m
Declination: -21 43.3199'
Apparent position at current epoch:
Right ascension: 18h13.306473m
Declination: -21 43.3800'
Dist from home planet: 2.92102671 AU (436,979,376 km)
Heliocentric position: lon 254.63901 lat 2.03944
Heliocentric radius 2.40879 AU
97.47% illuminated
Phase angle: 18.30 degrees
Elongation from Sun 50.03 degrees (morning sky)
Speed of apparent motion: 1.096'/hour at position angle 88.0
Motion is -0.44 degrees/day in RA, 0.02 degrees/day in dec
Preliminary designation: 1916 f
Discovery date: 1916 Sep 6
Discoverer's name: Nicholson, S. B.
Discovered at: Mount Wilson
Assumed asteroid diameter 7.9 km
Absolute magnitude: 15.0
Slope parameter: 0.15
Orbital arc: 30849 days
142 observations made to determine orbit
Orbit computed on 09 03 2001
Current ephemeris uncertainty (CEU) on 30 11 2001:
7.1E-02 arcseconds, changing by 3.2E-04 arcseconds/day
Next peak CEU: 1.5E-01 arcsec, on 21 04 2002
Maximum CEU in next ten years: 2.6E-01 arcsec, on 30 09 2003
--------------------------------------------------------
Comments from the MPCORB database:
Designation: (878) Mildred
Absolute magnitude: 14.6
Slope parameter: 0.15
Orbital elements:
Semimajor axis: 2.3600268
Eccentricity: 0.2263611
Inclination of orbit: 2.06067
Argument of perihelion: 189.90179
Long. ascending node: 172.87474
Mean anomaly: 267.09493
Mean daily motion: 0.27184958 degrees/day
Epoch of elements: 4 Jan 2010
Uncertainty level: 0
598 observations made at 16 oppositions
Orbital arc: 1916-2009
Last observed: 2009 06 16
RMS residual: 0.59
Perturbing objects used in orbit: M-v
Orbit computed by MPC
Orbit based on the JPL DE403 positions and masses
Reference: MPO169559
Perihelion distance 1.8258085 AU
Aphelion distance 2.8942451 AU
Period of orbit 3.63 years (1324.3 days)
Date of perihelion JD 2455542.25175 (11 Dec 2010 12:03)
======================================


[Non-text portions of this message have been removed]