Extension Tube 2″/2″ 80 mm

Extension tube 2″/2″ 80 mm

Every experienced astronomer knows that achieving correct focus is not always straightforward. Whether you have a Newtonian reflector with a short focuser travel, or a refractor you want to use for direct observation without a diagonal prism or mirror, you may find that the focuser simply cannot travel far enough to bring the eyepiece to the required distance from the primary mirror or lens. This is exactly where the 2″/2″ extension tube with a length of 80 mm comes in - a compact and reliable accessory that solves the problem elegantly.

When do you need an extension tube?

With Newtonian reflectors that have a short focuser travel, it is quite common for the focuser to be unable to travel far enough to achieve a sharp image - especially when using eyepieces with a longer eye relief or when imaging with a mirrorless camera. A similar problem occurs with refractors during direct observation without a diagonal mirror or prism, where the optical path without this element requires a significantly greater distance between the focuser and the eyepiece. The extension tube with an optical length of 80 mm compensates for this difference precisely and allows comfortable use with a wide range of eyepieces and other accessories.

Universal 2-inch compatibility

The tube features a standard 2″ connection on both the input and output, making it fully compatible with standard 2-inch accessories - eyepieces, filters, adapters and cameras. There is no need to look for any reducers or compromises. Simply screw or slide it into the focuser and attach your eyepiece or any other element of the optical chain to the other end.

Typical use cases

• Replacing a diagonal mirror with a direct adapter when the focuser cannot reach focus
• Connecting a CCD or planetary camera without using a diagonal
• Using eyepieces with a longer eye relief that require greater back focus distance
• Direct observation with refractors without a diagonal prism or mirror

The 80 mm length has been thoughtfully chosen to cover the most common cases of insufficient focuser travel. If needed, multiple extension tubes can be stacked in series to achieve an even greater optical length.

A must-have for every serious astronomer

This is an unassuming but very practical accessory that should not be missing from any well-equipped astronomical kit. Correct optical path length is a fundamental requirement for getting the full potential out of your telescope - and this extension tube helps you set it simply and reliably.

Technical specifications