Spot uses a program from JPL's Horizons called ISPY to do this calculation. JPL updated the interfaces to their web facing services and we have not had the resources to patch Spot so it can automatically talk to Horizons. So, you will have to run ISPY yourself to get the list of all moving targets that might be in the frame. If you want to plot those moving targets in Spot (as opposed to some other program) you will then have to email the list to help@spitzer.caltech.edu so we can load the ephemeris files for those objects into Spot for you (because Spot can no longer talk directly to Horizons and do it automatically).

To run ISPY yourself, you can follow the directions in Appendix 3 in

http://ssc.spitzer.caltech.edu/warmmission/propkit/sso/horizons.pdf

The email interface to ISPY does work, but many modern email clients are adding extra invisible characters to text because they assume they are talking to other modern email clients that can decode these characters and ISPY requires plain ASCII text emails. If you have trouble getting results back from ISPY, please contact them using the information found in the spec sheet for the software:  ftp://ssd.jpl.nasa.gov/pub/ssd/ispy_mail_example.long