The profiled bar under the tube that clamps into the mount’s saddle. The two standards are Vixen style (about 44 mm wide) and Losmandy style (about 75 mm), stiffer for heavy instruments. A longer bar gives room to balance the load.
Related terms
- Mount
The support that carries the instrument and lets you point it. It matters as much as the optics: at 100× the slightest wobble is magnified 100 times. Mounts are alt-azimuth or equatorial, manual or motorised.
- Counterweight
The weight fixed on a bar opposite the tube on a German equatorial mount. Slide it until the polar axis stays still when unlocked. Good balance spares the motors and improves tracking.
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