In article <4qbspe$46e@news.cc.ucf.edu>, clarke@acme.ist.ucf.edu says...

>Has anyone used this item?
[....questions/comments about use with telescope deleted....]
>Does the Vivitar change the seperation of the lens and camera
>or does it operate by moving elements around?

It is an excellent 7-element converter, with a focus helical added
(variable length extension tube at the front of the converter -
the glass remains fixed relative to the rear bayonette mount).
Hope This Helps