I used to use an old Vixen Polaris and the hand controller had a standard 2.1mm plug. I cannot remember the polarity but I did have to get a new hand controller after getting it wrong once. My Vixen hand controller was not polarity protected so if unsure check the inside first if possible.
I found the following links:
https://stargazerslounge.com/topic/3...-for-vixen-gp/
and
https://www.vixenoptics.com/category-s/117.htm
Note one plug option is centre negative and the other is centre positive (plus).