FYI
this image was taken using a Vixen Polarie.
Admittedly 15mm is not a lot of FL, but as you can see the stars are pin sharp
after a 2 minute exposure.
My Losmandy Starlapse carries more payload has decidedly lower periodic error (fitted with a high precision one piece worm block) but weighs a bit.
If you are looking for a tracker that will fit into a lens pocket of your camera bag, the Polarie works well.