The EQ6 is very capable of Astrophotography. one limitation of the mount is it's periodic error which can get quite extreme (+/- 20 arcseconds) but also can be reasonably good (-/+ 8 arc seconds or lower) depending on when it was manufactured, most of this can be overcome with guiding software. I have not used the GOTO hand controller but I believe it has some sort of PEC adjustment, someone with the HC can correct me if it doesn't.
I have taken a few images up to around 2 minutes of exposure through an 80mm F450mm Refractor, with really good results.
So this is really dependent on what you are carrying as well. I use a Skywatcher 8"f6 and 80mm F450mm refractor which only has a weight of about 12kg, so I am not overloading it any.
I use a different controller which is done via a PC. It's called EQMOD and many successful images have been taken with it, as long as you have access to a guide camera (toucam or DSI).. Down side to this is it is PC dependent so power is a must if you plan on staying out all night.
Some of my images can be found at...
http://southcelestialpole.org.au/blogs/astroman.php
Anyway wont bore you with details check it out at..
http://eq-mod.sourceforge.net
Test images by myself and others can be found at...
http://eq-mod.sourceforge.net/testimages
Documentation can be found .....
http://www.welshdragoncomputing.ca/eqmod/doku.php
Hope this helps some...