I will try to explain this as clearly as I believe to understand the
process. If you are using a MPCORB file, some of the data has been
updated since Guide 8 came out, hence the 14.6 mag. Turn off the MPCORB
selection in the astroid option and go back to the 878 Mildred. You now
see the older data stored in Guide with the MPCORB reference showing the
15.0 mag as (H). What you are seeing when using a new MPCORB file is
some new and old data mixed. Maybe Bill has a better explanation and can
be be more precise on the subject.


Denis

On 11/02/2010 4:05 PM, Ben Hudgens wrote:
> 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]
>
>
>
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