Looks like an Isolator. The ST-2000 has a self guiding sensor. Just plug this in line between the ST-2000 and the auto-guide port.
But I ask "what type of motor plugs do you have on your Gemini"?.."the old flat telephone type, RJ12 and cables/connectors" or "the newer round DIN type connectors"?
This is important!
This is important as the older Gemini units
must have the "opto isolator" in line between the guide head and the Gemini auto-guider port.
Page 42 of the Losmandy Gemini manual states:
IMPORTANT NOTICE:
(1) Never connect TTL output stages directly to the Hand Controller or auto-guider ports of an older version Gemini! Severe damage may occur to the connected devices. Use a Relay Box (as provided by SBIG)
(aka your opto isolator) or the optional Losmandy Optocoupler unit instead. By so doing, you get the additional advantage of providing electrical protection to these sensitive units.
..........
Detailed instructions for connecting an SBIG camera with TTL outputs to the older version of Gemini can be found in Appendix 8.6 (Autoguider Port).
Appendix 8.6 states:
8.6.1 Connecting Autoguiders with TTL Outputs to Older Gemini
Systems SBIG ST-237/ST-7/ST-8/ST-9/ST-10/
ST-2000 series cameras with TTL outputs must be connected using the SBIG Relay Box, the optional Losmandy Optocoupler or equivalent when using an older version of Gemini.
I don't want to scare are alarm you but.....you may have damaged your Gemini unit (or camera). I do not know enough to tell at the moment ....so you may be best to head over to the
Gemini Yahoo group for more info. Others more wise than me can chime in here....
Next...you stated
"...It's not a polar alignment issue as that's already been done with a polar alignment scope..".
In reality any polar scope alignment will not be accurate enough for imaging, you need to perform a "drift alignment".