At 12:03 2002-04-07 -0600, Stephen wrote:

>Asteroids seem to disappear on 2005 May 09. (Between JD 2453499.99922
>and 2453499.99923)

As Spock would say. "interesting"

Bill is going to have to answer this one for a full explanation as to why
guide takes a longer time to calculate the asteroid positions when the JD
changes over to 2453500 from 2453499. I assume that Guide has to go back
and get data from another table in the asteroid file on the CD, although
the file in question spans the Julian dates from 2453400 to 2453600. My
computer (533MHz) does take longer to step to the next time period if I
have the MPCORB table of asteroids turned on that if it is just using the
data from the CD.

The effect is much more pronounced if I have the "Direct to screen" turned
on because it blanks all of the asteroids as it starts to redraw them. If
the "Direct to screen" mode is turned off then the old positions stay there
until all of the new positions are calculated and then displays them all at
once. Hence you have the old positions on the screen and don't notice the
time it takes to calculate the new positions.

Why this occurs between JD 2453499.99922 and JD245349923 is a mystery.

It is amazing what one finds out by playing with Guide.

All the best,

Bob Elliott
750 Fall Creek