Focuser Extension Tubes

Extension tubes are used to extend the back focus of a telescope. This is sometimes necessary to compensate for the path length of a star diagonal when attaching a camera or autoguider to a refractor telescope. This allows the camera or autoguider to achieve focus. Schmidt-Cassegrain telescopes and their derivatives normally have enough focus travel to reach focus with the star diagonal removed. An alternate application is to allow an eyepiece to reach focus with a refractor in a straight-through configuration without a star diagonal. The Japanese actually prefer to observe this way, whereas we Americans seem to favor star diagonals. Ha ve a look at the images of Takahashi refractors and note that they are often shown with an extension tube and an eyepiece but no star diagonal.

Orion 1-1/4 inch Extension Tube

This anodized, machined aluminum 1.25" Orion Eyepiece Extension Tube provides extra focuser "back travel" sometimes needed to achieve focus with certain eyepiece / telescope combinations. More back travel is often needed for short-range terrestrial viewin

$19.95

Orion 2-inch Extension Tube

This anodized, aluminum 2" Orion Eyepiece Extension Tube provides extra focuser "back travel" sometimes needed to achieve focus with certain eyepiece/telescope combinations or when a camera is used without a star diagonal in place.

$21.95

TeleVue 2" Extension Tube

The TeleVue 2 inch extension tube is used to provide more path length or "out" focus. This may be needed to replace the path length of a star diagonal for straight through viewing, or to achieve focus in photographic applications.

$65.00

TeleVue 2" Eyepiece Barrel Extender

2 inch Eyepiece Barrel Extension - combine with 12mm TeleVue Nagler Type 4 eyepiece to make it parfocal with other Type 4 Naglers and allow the use of 2 inch filters.

$25.00

TeleVue 3-1/2-inch Extension Tube

The TeleVue 3-1/2 inch extension tube is used to provide more path length or out focus. This may be needed to replace the path length of a star diagonal for straight through viewing, or to achieve focus in photographic applications.

$65.00