Originally posted by Stone G. Wow. Some impressive photos on your site. To bad that many lenses have so much coma wide open. I have tried some with a Pentax M 50/2, but I have to close it to f5.6 to get rid of that coma. Now, I just wait for some good nights to test a Sigma EX 50/1.4.
About the tracking platform, I will choose the iOptron. One reason can be found in a detailed review made by one of the must trusted Sky & Telescope authors, Dennis Di Cicco, review you can find on the iOptron page
https://www.ioptron.com/index.cfm?select=productdetails&phid=febb7d36-d904-4...0-41a6103fae86
The other one, is that sooner or latter you will need longer exposure than those which can be offered by the Pentax O'GPS, which, by the way, is good, and cheap, but has his limits.