Originally posted by Gimbal I guess so.
But you do realize that wide rectilinear lenses distort the image? A star that appears to move say 4mm in the center of the frame during a certain shutter speed, will move 6mm if you reframe so that star sits in the corner for the same time. (The numbers are of course just examples taken out of the blue to illustrate the problem.)
Yes, a wide rectilinear lenses will distort the image. However, the real question here is to Pentax. Please identify your sources of error, to what extent do they contribute to the overall problem and for each source - how is the error manifest/realized in the resultant image. AstroTracer is a closed black box system. We know the generic inputs, we just do not know the quality (accuracy and precision) of the inputs (for instance the compass). Are there limitations to the system? - absolutely! We know that exposure time is one (Pentax has limited that to a maximum of 5 minutes based on focal length), and that times of less than a minute minimize star trailing. That is a substantial difference. Through observation (actual use) elevation angles beyond 45 degrees produce degraded results, and Pentax should acknowledge and quantify that. Your position is that wide rectilinear lenses is a major contributing factor - OK, Pentax needs to characterize and quantify that aspect (what focal lengths minimize trailing). My position has been that the compass has limitations and needs to be characterize and quantify - and potentially address how an extended calibration process may help to control this.
Once sources of error have been identified, characterize and quantify and their effect/how they will be manifested in the resulting image - Pentax should be able to advise possible approaches to reduce or to minimize their effects. They have done this in one area - fine calibration should not be done near large metal objects - cars. They can also update the system - either in firmware (to the extent possible) or with new hardware (camera bodies - for instance the K1 and its new 5 axis stabilized sensor).
Pentax can also publish a technical paper addressing their overall system in a more technical environment than what they currently have. A several page paper addressing the system, inputs, characterized errors, what and how users can assist in their minimization, etc. For instance - a discussion on exposure time, focal length, are a couple - and there are several more.
Pentax has modeled the GPS system. Addressing the model (to the extent possible) along with its implementation within the actual device (O-GPS1/K3II/K1) utilization would do a great deal in addressing this topic.
Quite frankly - I don't want to do it. Users should not have to reverse engineer a system in order to use it effectively. I retired several weeks ago and just want to go take pictures and improve my composition. My days of system architecture and engineering to a large extent are in my past. I have done several star tracking systems - across a wide range of uses - (hybrid combinations of GPS, inertial and celestial) from sub-orbital navigation, orbit insertion, station keeping and re-entry, to even a little telescope down in Texas.
Right now, I am trying to decide if the weather is good enough to drive up to Flagstaff today to shoot the fall colors up in the alpine meadows. My only concern right now is aspen, birch, maple and oak.