I want to plot a series of X-Y points on a scatter chart
that represent the position of a satellite at a specific
time. X-axis is Right Ascension (RA) and ranges from 0:00:00
to 23:59:59. Y-axis is Declination (Dec) and is -90 to +90.
X crosses Y at 0. I have no problem plotting the points, but
I want to add the local time at which each point occurs as a
secondary X-axis and can't figure out how to do it.

Can anyone help? Thanks.

Mike Hogan