I read about C/2017 O1 ASAS-SN. As this comet is currently nice and high in the sky (at least in the second half of the night) I decided to give it a shot.
First, I just pointed the mount to the point in the sky where the comet is and started imaging:
(OK, ignore the dust motes for a second :-) But you can clearly see the comet in the middle right. Zoomed in:
Yep! There it is. But of course elongated as the scope is tracking the stars - not the comet.
So, I used Horizons (part of APCC Pro) to track the comet. I think Ray Gralak did a great job with Horizons. It's a little complicated at first to setup, but once you went through it once or twice, it's actually very easy!
With that, now, my images looked like this:
The comet is in the middle - and you can already see that the stars are elongated. Zoomed in:
It looks as if Horizons adjusts the mount only every few minutes (these are 10 minute exposures) ...
... on second thought, this could also be my PEC gone wrong. Tonight, I'll try 10 minute unguided exposures with and without PEC to see what happens ...