The AstroMaster 114 models have a 1000 mm focal length. Why are the tubes only 508 mm long? Is this a mistake?

No. Both tubes are identical in optical design. The reason the tube is so short is because the optical design incorporates a Barlow lens built into the focuser. This lens extends the focal length of the primary mirror and the telescope without adding physical length.

The result is both models feature a compact tube Newtonian reflector with a long focal length.

Updated 12/25/13