During an imaging session this fall, I attempted to create a custom tracking model with my Mach2 and GTO keypad. After some fiddling and experimenting, I was unsuccessful, but a two-minute test image showed round stars even though I was using no tracking model at all. So what the heck, I tried a couple hours worth of unguided 4-miunte subs, and while not perfect, the results were satisfying. In the attached image on the top row, you'll see the California and Heart nebulae taken from a Bortle 7.5 backyard in Milwaukee, using an Optolong L-eNhance filter and a QHY 168C one-shot color camera. I used a Nikon 300mm f/2.8 lens for these two. The bottom row shows the Soul nebula using my Sigma 500mm f/4.5 lens, and the Flaming Star with the same lens and a 1.4x teleconverter for 700mm of focal length. I use only my calibrated RAPAS for polar alignment. I'll continue to apply a custom tracking model when time permits, but with wide field imaging, the unassisted Mach2 tracks very nicely.
Ernie Mastroianni