This is my first blog post in a very long time.. too long to be honest.
At the end of the observatory maintenance trip the whole team returned to the UK and buried our heads in paperwork and attempts to make the system run well.
Whilst on the trip we did a large amount of work diagnosing problems with the mount pointing; by the end of the trip it looked as if we had got a good handle on the problems causing poor pointing.
The primary of these problems seemed to be with homing the mount. After a substantial amount of diagnostic work and help from the guys at Software Bisque, it looked like we had solved the homing issue.
On our return to the UK we were less than excited by the pointing performance that the system was delivering. Since then I have worked with Chris to continue documenting and testing the mount's problematic performance.
At the moment we appear to have two problems affecting the pointing at once.
The first of these problems appears to be linked to the homing of the mount once again. At start-up the homing of the mount can either be correct, or shifted by a fixed amount in the Dec axis. As we cannot currently find a solution to the homing issue, we are working around this by manually adding an offset to the telescope pointing when the homing offset is detected. This is less than ideal, but it is keeping the telescope pointing within acceptable boundaries whilst we work on a long term solution.
The second of the problems is with the tracking of the mount. Once the mount has finished slewing there is a delay of around 60 seconds before the mount actively motors around 4 arcmin in Ra away from the target, then returns to continue correctly tracking the object within a further minute. This problem appears on the images as trailing. The delays that precede the error and return slews are variable, but the actual slewing happens in a period of seconds... substantially faster than the tracking rate of the Ra axis. We have absolutely no explanation for why this is happening; we are currently working around this with an exceptionally long post slew settling time.
I am currently working on a plan to replace the mount on site with our second Paramount ME.. More posts to follow on this subject soon..