...and just as well Marcus... If your EM400 was over the manufacturer specs you'd want a quick sale and get another (or alternative mount). Tak mounts don't support PEC, so forget about PEMPro. The performance you get, you're stuck with. IMHO this is a disadvantage. I know someone will quickly respond and say, yeah they're built so good they don't need it or who cares I autoguide anyway. That's fine if you want to think along those lines.
The build quality statement just doesn't fly. The PME would have a similar or slightly better build quality...and it supports PEC. If you take the PEMPro stats - sampled out of 11 PME's the average reduction of peak-to-peak PE using PEC went from 3.8" down to 0.8". Enough said. (
http://www.ccdware.com/products/pempro/examples.cfm). Don't understand Tak's theory here. PEC isn't too hard to support.
Secondly, indeed autoguiding will counteract PE problems...but that's not the point. The more you can reduce your mounts PE before autoguiding is a major advantage. The less autoguiding corrections made, the less chance of error i.e over/under corrections etc. As you increase your focal length, you'll quickly realise this is very important. Your TOA-150 is a wide field instrument so the tolerance is quite high. Pushing the 2500mm+ boundary starts getting serious.
Will try upload some stats from the Titan I have. I recorded PEC over six months ago so may still have the figures. If I recall correctly, after PEC I experienced a peak-to-peak of ~1.8". Out of the box it operated at -/+ ~4.2" (still under manufacture specs of 5.0"). Thus a considerable improvement.
Moral of the story...don't underestimate the power PEC will deliver when it comes to imaging. If I could afford a mount that didn't need to be autoguided while operating at 3000mm+ focal length (such as the
NTM-500 that has a tracking accuracy of < 1" over a 120min period, not to mention the 0.3" when guiding), I'd have a huge smile from ear to ear.
