Re: ISS magnitude

Ed Cannon (
Wed, 30 Dec 1998 01:25:37 -0600

Jim S ( wrote:
> Has anyone determined an "intrinsic magnitude" value for the current
> configuration of the ISS that can be supplied to the "QuickSat" program
> to produce reasonable visible pass predictions?

For Austin, Texas, predictions on his Web site -- (e.g., Dec. 25), Mike McCants 
is using +1.0, which I think converts to about +2.5 in the Molczan 
system, and +3.0 Molczan converts to +1.5 for Quicksat.  (There's 
some discussion of the conversion at under "Magnitude 
of Brightness Associated with a Satellite".)  I've put +0.5 in my 
own quicksat.mag file.  I wonder what its intrinsic mag. will be in 
a few years....

I believe that one thing to consider is that, so far at least, the 
phase angle is pretty important.

On Christmas evening (i.e., late on 25 Dec. local time), my sister
and I observed ISS from my folks' house in San Antonio, Texas, and, 
since they couldn't make it home from a day trip in time, my parents 
saw it from alongside a highway a few miles away!

Ed Cannon - - Austin, Texas, USA