I'm sure this one will stump many users, but this is an excellent accessory for those who are using a spotting scope mounted on a conventional tripod for some astronomy. Since stars and planets are constantly moving out of the field of view, you must manually unlock the tripod head, refind the object, then lock down again. This also becomes a big problem at higher magnifications because you tend to over compensate, so it may take several tries to recenter the object.

The idea of adding a fine adjustment mechanism to a camera tripod is not new. I have been using them for years on my small Televue refractors. Problem with most slow motion accessories is they make the scope sit even higher off the tripod and cuase balance problems. The Vixen AM-FA-8798, though, is different. It has a very low profile and is also of high quality, as you would expect from Vixen. I have been using one for a few months on the rare clear nights around here to see wide angle views of open star clusters and it makes life a lot easier.