So can this tracker take 4 to 5 min subs say with a 200mm lens? If you can only get 60 sec subs might as well make a barndoor tracker and save yourself the money.
Stay tuned for testing that very thing. Just don't know yet, and sorry I have not had time to test this myself
But a home built barndoor is certainly an option. Lotsa plans, descriptions, etc. out there to get you going. One of the main benefits of the StarTracker to me, was the way iOptron implemented polar alignment. First, the PA scope comes with the unit, at the price I mentioned earlier. That may, or may not be the price now. But I think it is still cheaper than Polarie. Second, it has a notch in it to allow the "on" LED (red) to shine into the PAS, illuminating the concentric circles which indicate placement of Polaris. And they make an iPod/Pad/Phone app that determines where Polaris should be giving iPod owners a very quick way to determine the placement of the celestial pole quickly. Haven't tried that yet either (need to update the OS on my 'pod). Third, the PAS is not located in the camera mount ring. It is off to the side so you can continue to use it-- and fine tune polar alignment-- once the camera is mounted. Fourth, the SkyTracker's built in altitude "hinge" means you do not have to set altitude with the tripod ball head or geared head or whatever. It's built in, lessening expense for a ball head etc. And, the implementation of a geared knob to set altitude is, IMHO, easier. It also means less equipment to carry if portability is important to your use. (It is to my use). 4 AA batteries as opposed to 2 (I think) for Polarie. But the ease of polar alignment is key for me, as is portability.
I think that the Polarie is a great unit, as is a well made barn door tracker. Choice, choices. For that matter you can likely find a nice CG-4 mount for about the same or less money. Not so portable though. Just food for thought, folks, food for thought.
When I have time to get out there, I plan to test the length of subs. As for a 200mm lens, I don't know. Again, it is all about what DSLR you are using, etc., and the combined weight of your specific gear. The Kenko SkyMemo and the Losmandy StarLapse, I believe, have higher limits for loading, so those could be considered as well, if you have the $$$.
Hope this info helps. As I said, stay tuned !