Projector

This is an offset type projector which means the projected image if offset from the lens, not centered.  This style allows better projection without degrading resolution from keystone adjustments.  This image from the user manual better explains:

While this projector user manual doesn't specify it's throw ratio, the above table was used to figure out the distance I wanted the projector to be from the table.  As this was longer than the distance between the table and the ceiling, I needed to use a mirror.

Testing

To double check the distances and that the system would work well, I mocked it up upside down.  That is, the projector and mirror were on the table, and projecting on the ceiling.

(The ceiling image looks distorted due to the camera angle.  It was orthogonal on the ceiling, and carefully measured to confirm the image was good)

Mount

I repurposed an old projector mount I had for this.  It was intended for a different projector, but made a steel mounting adapter, cutting openings for ventilation.  As it was a little rusty and black, I painted it white to better blend in with the ceiling.  This was important because I might want to remove the projector, and this will be less obtrusive.