At 21:40 2003-03-07 +0000, Lawrence wrote:

>When doing astrometry and analysing the results, I am sure that I recall
>that Guide has a facility to plot residuals. Can't find this on the
>'Extras' page - can someone jog my memory?

I don't remember plotting the residuals in Guide but I do turn on the "MPC
observations" in the "toggle user data sets" in the Extras dialog box.
That plots each observation that you make and reduce with Charon and save
to the MPC.log file.

Before I make the observations I add a trail for the object and ask for a
tic mark each hour or less if it is a fast mover. Be careful to set the
time to an even hour before adding the trail. In the USA I usually set the
time to 0h UT since almost all of my observations are after that time and I
add trails for each target that I intend to observe that night.

You can then see the exact location of the object and its calculated
position at any time. This is a way of getting an "O-C" for each observation.

Don't be alarmed with any disparity that seems to be consistent from one
observation to the next. Consistency is more important than the actual
residual.

An observation that seems to be way out of line is a good candidate for a
"Graff-O-Gram" and should be deleted before sending to the MPC.


Bob Elliott
750 Fall Creek