The VC Extension Tube from Vixen Optics adds 2.6" (66mm) of length to the optical path of telescopes with 60mm diameter drawtubes.
An extension of the optical path is often necessary for applications involving prime focus imaging, so that the image-receiving device can be placed at the correct distance from the objective to achieve focus.
This extension tube is also useful for observing with Vixen's Japanese-made refractors (ED*S series, A80SS, NA140, etc.), so that you can use a 1.25" 45° or 60° diagonal directly on the back of the scope, instead of being attached to the straight-through path of the flip mirror which is included with those telescopes. Doing so lowers the size and weight of stuff you've got to take in the field, and also allows less internal obstruction for the viewing. To do this, combine this VC Extension Tube (screwed directly to the back of the telescope's focuser barrel) with the #3725 EA 60mm to 2" adapter and a typical 2" to 1.25" reducer (such as Tele Vue's #ACF2125, Lumicon's #LA1045, or Zhumell's #2125ADAPT).
You will assuredly need this tube if you are using Vixen's 3878 Direct Wide Photo Adapter with any Vixen refractor telescope.