The 8SE is on an alt-az mount. There is (no longer) any commercially available wedge for it, so if you don't have one already, you will get field rotation, and the autoguider won't be able to correct for this. The SE single arm fork mount also suffers from fairly significant backlash.
I love my 8SE for visual, but for astrophotography, it's really not up to the job. You need a GEM. I never used it for more than 30 sec unguided subexposures. Here is an example:
http://www.astrobin.com/98885/
You can use the 8" SCT OTA with a GEM (I use the AZ-EQ6), and leave the SE mount for grab-n-go visual.