1. a tube that slides in and out of another tube, used in optical instruments such as telescopes and microscopes to adjust focus or magnification
Usage: technical; also called draw tube
2. a sliding tube in a surveying instrument or other precision apparatus that allows for extension and retraction
Usage: technical; surveying

Examples

• The drawtube on the microscope allows the user to adjust the distance between the objective lens and the specimen.
• By extending the drawtube, the telescope's focal length can be modified for clearer viewing.
• The surveyor carefully adjusted the drawtube to ensure accurate measurements.
• A damaged drawtube can affect the optical quality of the instrument.
• The drawtube mechanism must be kept clean to prevent scratching of the internal surfaces.