1. Plural of drawtube; sliding tubes in optical instruments (such as telescopes or microscopes) that can be extended or retracted to adjust focus or magnification.
Usage: technical; usually plural

Examples

• The microscope's drawtubes allow the user to adjust the distance between the objective lens and the eyepiece.
• By extending the drawtubes, the astronomer could fine-tune the telescope's focus.
• The vintage telescope featured brass drawtubes that slid smoothly within the main barrel.
• Careful handling of the drawtubes prevents damage to the optical alignment.
• The drawtubes on this instrument are marked with distance measurements for precise adjustment.