Doug,
unguided imaging with anything less than an ap or paramount is unrealistic. Everyone autoguides because pec is not perfect. There are a number of issues.
Firstly with the eq-6. This is a mount built to a budget, most have a pe of under +/- 10 arc secs. However while the general profile is repeatable there are variations between the individual teeth of the worm gear that cause slight variations from worm cycle to worm cycle. In addition there are small random errors of an arc sec or so caused by roughness in the actual worm. There are also variations in spacings of the worm wheel from the worm due to manufacturing tolerances that can lead to the exaggeration of these random errors. The actual worm gear is not hobbed with an exactly matching profile to the worm. This allows for greater freedom in putting the mount together, but exaggerates the pe when there is a tooth to tooth transition. These things are typical of mid to low end mounts.
Essentially what I'm getting at is that pec assumes that the gear errors are perfectly reproducible, and I've given reasons why in the eq6 they aren't.
Below is a link to a survey of improvements from pec from the PEMPRO site :
http://www.ccdware.com/products/pempro/examples.cfm
You will note that none of the mounts has zero pe despite having programmed pec. Though I gotta say several are pretty damn close and below my seeing levels in Melbourne!!! But most of these mounts would not be able to take lengthy unguided images unless it was at a short focal length....
Recording pe for correction is difficult. Everyone forgets that when recording pe for correction you have to see the error occur, then issue a correction. This takes time, the mount may have already moved further after you issued the correction, you are always chasing the error, and always behind it. So when you program it, it replays always a fraction late (unless you've a means of editing and shifting the timing of the pe corrections.) Hence you are unlikely to be able to image for any long period of time.
Generally the eq6 is a good mount - I have had one that was superb, and have another that is a total dud, - and awaiting parts from Tasco to fix it (They have been very pleasant to deal with and I have no gripe with them at all) - and I have another friend with one that is just as good as my first one was. It is through analyzing this mount that I learned much about gears and pe.
BTW, you do not need an expensive extra scope to autoguide, go to:
http://www.skyinsight.net/astrophoto/current.php
and download the latest issue (free) and read the article on building a compact robust guidescope with a 40mm objective!!!
hope this helps
fwiw
Gary