There isn't really another common name for the body tube in a microscope. It's simply called the body tube or sometimes the main tube.

However, here are some related terms that describe parts of the microscope:

* Arm: The part that connects the body tube to the base.

* Stage: The platform where the slide is placed.

* Nosepiece: The revolving part that holds the objective lenses.

* Objective lenses: The lenses that magnify the specimen.

* Eyepiece: The lens that you look through to view the magnified image.

So, while there's no specific synonym for "body tube," these terms all relate to the structure and function of the microscope.