Here’s one of the first images from the batch of images I shot of Comet Panstarrs on March 11, 2013.  I used a 200mm F/2.8 Canon lens with a Sigma 2X Teleconverter, for 400mm of focal length at F/5.6.  This was a 1 second exposure @ ISO 400.  The camera was riding on an old German Equatorial mount (a CG3 clone) with a clock drive.

Comet Panstarrs with a 2 second exposure @ ISO 400, Canon 200mm F/2.8 w/Sigma 2X Teleconverter, Canon XS (modified) DSLR.

Here’s one of the last shots before the comet sank into the murk.  I couldn’t even see it anymore with the binoculars, but the camera picked it up with a 10 second exposure.