Back home and saw the moon hanging low in the sky, I got the chance to try out the Astrotrac with my Orion 100ED. I secured all the joints but when I put my 100ED OTA on it (without the lens), the 3/8" screw just slips. With just a simple screw to fix the 410 head, I found that it cannot hold the heavy weight at all.
The verdict is out, I shall keep my TG-SP II since the apparently more capacity of the Astrotrac does not work in my case. At the same time, I shall also further lower the price of my Orion 100ED f/9 since I ain't going to get a mount enough to use it. In the mean time, I will keep the Orion 100ED f/9 first so that I might be able to do some visual scanning with my Unistar Lighter. But the Astrotrac is going to be sold. Don't get me wrong, there's nothing bad with it, it just couldn't fit my original intended purpose.