| The TeleVue 2" Eyepiece Barrel Extender increases the telescope back focus distance when you cannot rack out your focuser enough to reach focus with certain TeleVue eyepieces. It also provides a mounting location for 2" (48mm) eyepiece filters to let you use your 2” filters with dual 2”/1.25” barrel eyepieces, such as the Ethos series.
The extender can also help parfocalize certain eyepiece combinations. For example, with the extender, the TeleVue 12mm Nagler Type 4 becomes approximately parfocal with the 17mm and 22mm Nagler Type 4 eyepieces when used in a TeleVue 2" diagonal.
The field stop of the TeleVue 55mm 2” Plössl is located near the bottom of the chrome eyepiece barrel. This means that you have to rack your focuser out further relative to most other eyepieces, such as the 27mm TeleVue Panoptic, when using the 55mm TeleVue. If you find that you cannot rack your focuser out enough to achieve focus when switching between the 55mm and other eyepieces, adding the eyepiece extender to the 55mm will make the TeleVue 55mm Plössl eyepiece approximately parfocal with the TeleVue 27mm Panoptic and most other 2” eyepieces. |
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