In reply to sbc_10:
Thanks for the comments.
I used to piggyback the camera on my telescope (which had alt az mount) but tried an Ioptron Skytracker and it had more accurate tracking and as an equatorial mount, doesn't suffer from field rotation and I've never put the camera on the telescope since! At 200mm, I think I could push 2 minute exposures on a windless day. 50mm will go to 5 minutes OK but the sky isn't dark enough here. The mount is very portable, and much less expensive than a full telescope mount. I look forward to going out camping somewhere a bit darker and taking the camera one weekend!
That image was from last Thursday and it was very windy so I'm pleased with that. It was made with 40 30 second images stacked, but the comet is very clear in a single 30 second exposure.
Here's the mount:
http://www.ioastronomy.com/product/ioptron-uk-skytracker-3302w-combo
The lens is an old Nikon AIS 200mm F4 prime on Nikon D5300. Hardly in the same league as a dedicated APO telescope, but very useable and common on ebay.
I time the exposures with a bargain MC-36b Nikon knockoff timer from China (about 1/8th the price of the real Nikon timer and works with their modern cameras unlike the genuine timer...)