(This is a "for the record" posting, not a "hey, look at my amazing photo!" posting. Explanation copied from Facebook, for non-experts; experts won't be interested in this photo anyway!)
This is my first *guided* shot using my star tracker. Star trackers, and simple complete mounts, are designed to rotate with the stars, but don't have any way of compensating for errors, either in the alignment to the North Pole (a big deal) or errors caused by variations in the motor drive running a tad fast or slow. With guiding, you use either an external second scope (which I'm doing) or part of the light from your main scope, and pick a star and adjust the mount to keep it in the same place in the frame. That used to be done by hand, and I tried it a few times but never got good at it. Now it's easy to do using a digital camera and some processing.
I recently got a ZWO Asiair Plus controller, and a small digital camera and small scope designed to be the guidance system. I'm using a Canon 5D Mark IV DSLR (30 megapixel) and a Redcat 51 lens (250mm focal length, f/4.9). I still have a couple of minor things to do: I want to get the camera astromodded, which will make it more sensitive to deep red/near infrared light and gather much more light from those deep red nebulae, and I need a light pollution filter. Finally, this camera chews up batteries like crazy, a Canon brand name battery barely lasts two hours. So, I want a rig that will power the camera more directly. After that, I think my life is complete...for the time being .
So, this is my first shot with my essentially complete rig. The point of this was to test the setup, not get a first-class picture, but all the same that dust spot right next to the Horsehead Nebula is killing me!!! I need to clean the sensor. When the battery runs out and I have to change it, the camera attempts to clean the sensor, but what it really does is move the dust around, ruining my ability to get adequate flats. Gotta clear the sensor before my upcoming shooting trip.
This is 53 minutes of data, taken from our veranda at our house in Kamakura: bright suburban skies, scope is set up next to the AC/heater unit which vibrates, and our house literally rattles when trains go by (about 250 trains a day). So I wasn't expecting anything at all useful, so I'm pretty happy that I have demonstrated the potential for the equipment.
This is the full stacked frame, no cropping, so you can see what's happening in the corners and edges. Even with polar alignment right around 2 arcmin (done using Asiair Plus's all-sky polar alignment; our veranda has no view to the north), over an hour or so it drifted a few pixels.
Still so far to go...