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Vixen versus Losmandy dovetail bars explained

A telescope attaches to its mount through a dovetail bar, and two widths dominate: the narrow Vixen style and the wide Losmandy style.

What a dovetail bar does

A dovetail is a bar with angled edges bolted along the telescope tube. It slides into a matching clamp, the saddle, on the mount head and is locked down. This standard interface lets a tube move between compatible mounts and lets you slide the tube to balance it.

Because the bar and the saddle must match, the dovetail standard is a genuine compatibility point, not just a bracket.

The two standards

The Vixen style, sometimes called the narrow or standard dovetail, is about 44 millimetres wide and is the common choice for small and medium telescopes and lighter mounts. The Losmandy style, also called the D or wide dovetail, is about 75 millimetres wide and is used for heavier tubes and larger mounts where the extra width adds rigidity.

The two are not interchangeable directly: a Vixen bar does not fit a Losmandy-only saddle and a Losmandy bar does not fit a Vixen-only saddle without the right hardware.

Dual saddles and adapters

Many modern mount saddles are dual-fit, machined to clamp either a Vixen or a Losmandy bar. If your saddle is a single Vixen or single Losmandy, you must match the bar to it, or fit a saddle upgrade or an adapter plate that carries the width you need.

When adding a bar to a tube, check the ring spacing and the bar length so the fixing holes line up and the tube can slide far enough to balance on your mount.

Choosing a bar

For a light tube on a small or medium mount, a Vixen bar is standard and sufficient. For a heavy tube or a large equatorial mount, a Losmandy bar gives more grip and stiffness and reduces flexure, which matters for imaging. Match the bar to the saddle your mount actually has.

Related

Sources: Losmandy dovetail standard documentation · Vixen mounting specifications