Hi Jim and Melita,
Yes, I was trying to create a custom coordinate system. I'm able to change the central meridian (180), but not the range (0 to 360, positive west).
The coordinate system is based on SimpleCylindrical_Titan, with the following ranges and radii:
CenterLongitude = 180.0
EquatorialRadius = 2575000.0 <meters>
PolarRadius = 2575000.0 <meters>
LongitudeDirection = PositiveWest
LongitudeDomain = 360
MinimumLatitude = -90.0
MaximumLatitude = 90.0
MinimumLongitude = 0.0
MaximumLongitude = 360.0
Christine