Inspeqtor wrote in post #18063376
As for leaving a star trail.... I did not think about mentioning ( I should have thought of this!) that I am using my iOptron star tracker! It was not a perfect alignment as I do see some trails....
Assuming you are able to get it aligned well, you should definitely try longer exposures using the iOptron. I've heard of people using exposures near 60 seconds with it. It's not worth owning a tracker if you don't take advantage of the longer exposures it allows.
If I had your setup, I would try to shoot 17mm at f2.8 (f3.2 if you find your lens to be too soft at f2.8), ISO 3200, for about 45-60 seconds. Get the exposure to be in the middle of the histogram, and then drop the levels down when post-processing the image.
I would also try one at a much longer exposure (and lower ISO), to see how well the tracker is doing. Maybe the same 17mm f2.8, ISO 800 (or even 400) for 120 seconds.
Judge the star trails by how long they are when viewing the image fitting to your screen. When pixel peeking at 100% crop, you might still see trails, but if you don't see trails when viewing at regular screen size, you're doing just fine.