tele-extender

tele-extender

(tel-ee-iks-ten -der) An optical device located in an extension tube on a telescope and used with an eyepiece in order to increase the effective focal length of the telescope and hence increase the image scale.
References in periodicals archive ?
Low quality extension tubes or tele-extender could break or give way to the weight of extended macro lens.
Flash equipment featured the Metz CT 45 with tele-extender, which he described as the ultimate potato smasher, Nikon SB-800 and Nikon R1C1 Close-up kit with three flashes.
Consider the purchase of a good Barlow lens or tele-extender to increase your telescope's magnification.
The last category of adapter is the tele-extender. This works only with Maksutov- and Schmidt-Cassegrain telescopes, which focus by moving the primary mirror back and forth.
An inexpensive way to double the focal length of your telephoto lens is to attach a 2x tele-extender ($30 and up), which fits between the lens and camera body.
For this reason, tele-extender is not recommended to use on slower lens like f3.5 lens or lower.