Hi Tom, > Just happened to be outside and caught a pass of something very bright > and fast traveling from SSW passing through approx. 30 Degrees ESE > headed to NE at about 19:15:00 EST. Sorry I don't have more exact times > and directions. This was definitely STS-92. Not bad considering the sun was only 4 degrees below the horizon. Predicted magnitude was about -2. --Rob Which reminds me, I need to go into SkyMap and change the phase equation for satellite brightness. For years (more than a decade?), it seems like everyone has been using a (1-COS(Phase)) factor to determine satellite magnitude from the standard magnitude (90 degree phase, 1000-km range). I used to have the correct phase function in there, but someone talked me out of it in the early 90's. While working on a related photometry problem, I had to solve the same double-integral that applies to this diffuse-reflector problem, and ended up "rediscovering" my original equation. If any other satellite prediction programmers are using this cosine dependence on phase angle in their software (phase here defined as 180 for full, 0 for new), I'll be happy to supply you with the correct lambertian function. The difference between these phase functions is not insubstantial, especially near opposition and at poor phase angles. (At opposition, the cosine formula is too dim by 0.5 magnitude; at 45-degree phase, the old formula gives predictions that are too bright by 0.7 magnitude). ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www2.satellite.eu.org/seesat/seesatindex.html
This archive was generated by hypermail 2b29 : Thu Oct 12 2000 - 18:09:20 PDT