Re: Standard Magnitudes

Rainer Kracht (
Wed, 29 Nov 95 23:13 +0100

>From: Ted Molczan <>
>Subject: RE: Standard magnitudes
>Date: Wed, 29 Nov 1995 11:43:22 -0500

>Also, 90 degrees seems to be well established among British observers, 
>who arguably have been the world leaders among amateur satellite 
>observers, so perhaps we should respect their de facto standard.

There is one more reason to keep this standard: you can't observe
Earth satellites at zero deg or even close to zero deg phase angle,
because the satellites are then in the Earth's shadow!

So every specification of a standard magnitude at zero deg phase depends 
on the way how the lightcurve is extrapolated. The standard magnitude at 
90 deg phase angle is (in most cases) part of the observed lightcurve and
thus more reliable.

If you assume that the two Lacrosse satellites are of the same size and
have equal standard magnitudes you can see the effect. From Russell's
observations I got:

standard magnitude for zero deg phase: 2.97 and 3.10 (difference 0.13)
standard magnitude for  90  deg phase: 3.62 and 3.66 (difference 0.04)

Rainer Kracht