The Kowa TSN-VA2B is a digiscoping adapter which isn't used together with an eyepiece-it is used instead of an eyepiece and projects a long, consistent beam of collimated light for use by digital point and shoot or video cameras.
The TSN-VA2B has built-in 14x magnification with the TSN-88 or TSN-77 series spotting scopes and 12x with the TSN-66/TSN-60 scopes. It attaches directly to the 88/77mm scopes like an eyepiece, but the 66mm/60mm scopes will require the TSN-CR3 adapter between scope and eyepiece.
The TSN-VA2B is a revision to the now-discontinued TSN-VA2, with superior optics but otherwise much the same function. The extremely-long eye relief of 100mm allows nearly any camera to work without vignetting; you must attach a DA series adapter ring to your camera's filter threads and away you go. While any digital non-SLR camera with 28-72mm filter threads works, the VA2B was designed around the exceptional digiscoping performance of Casio's Exilim Pro EX-F1 and even have a dedicated support bracket (TSN-PS2) for the combination.
All ventures in the world of digiscoping require the use of a sturdy tripod, first and foremost. You must take great care to keep vibrations during exposure to an absolute minimum. Adding vibration suppression pads below your tripod will increase your chances of success and employing a cable release, electronic release, or remote control for tripping the shutter is absolutely necessary.