[PRejto (Peter)]

I'm not having any major issue in guiding with my MEII, but I've always noticed that the X and Y plots in the guiding graph look different. Since I normally previously aligned my guide camera to North up (Position angle =0) the X plot is aligned with RA and Y with Dec. My thinking has always been that this would make it easier to diagnose an issue with a specific axis. I still think this is generally true. Differences that I saw I would assign to a particular axis. That seems reasonable and is common practice.

Then, due to the fact that CCDAP doesn't seem to like the guide camera positioned this way, I moved it to a PA =45. Now neither axis is aligned with RA or DEC. At first I thought this was a pretty bad arrangement but then I had the thought that actually this might prove quite useful in thinking about issues that I see and many others are trying to talk about on the Software Bisque Forum. The issue seen is that of random spikes in guiding seen pretty much mostly on the guide graph in one or the other of the axis. Now, with the camera aligned such that X=RA, one might assume that a spike in RA tracking is caused by some crud on the worm or something like that. However, with the camera at PA=45 PE, crud etc would cause a spike in both X and Y, not just one or the other.

Just the other night, with my guide camera at PA 45 I had very tight guiding along X, but major clumping and numerous spikes along Y. Sometimes a spike would show on both X and Y but that might happen only 1 in ten or more times. I cannot see how to reconcile these observations. Any mechanical issue from either axis show show a movement in both X and Y. Atmospheric movement should on average move a guiding star around randomly. If all is well I would expect to see on average pretty much the same thing on both X and Y. I don't see this so I can only conclude that my thinking about this is incorrect, or there may be an issue about the way guiding corrections are implemented in TSX. Others are speculating that there is some problem of the interaction between Protrack and guiding. I have attempted to improve what I'm observing by changing just about every parameter I can think of including exposure duration, delay, different guide star, aggression, min/max moves, guide correction rates (in Bisque TCS). The effect I see does vary with where I am guiding. It's best on the meridian and gets worse as I track to lower and lower altitude. Of course, seeing and guiding get worse with decreasing altitude but again I would expect to see it get worse in both X and Y. It gets a lot worse in just Y. In any case this is not a critical problem (for me) but seems to be for others on the forum at Software Bisque. What I'm mainly interested in hearing about from others here is if my analysis and expectation of what I should be seeing vs what I am seeing (with the guide camera at PA=45) is reasonable. I might be missing something obvious. Thanks for any feedback!

Peter