Here is 64P/Swift-Gehrels, a comet that was near M33 recently. I missed it then, but I finally caught up with it Saturday night, Dec 1, 2018.
I used 4 minute subs and I could have gone even longer at this location, but my guiding was iffy with bad seeing. Out of 20 minutes of subs, I lost one, so this is only 16 minutes of exposure.
Since it was so few, I just stacked the subs once while aligned on the stars and then used one sub of the central core to hide the streak caused by the comet’s movement in the sky. A quick and dirty star-freeze job. lol 🙂