Jasem,

I am currently developing an Alt/Az driver for a "dumb" Alt/Az mount that does not have any built-in capabilities — it just takes position commands and feeds back encoder position. To enhance its functionality, I have been integrating the Alignment subsystem into the driver. During this process, I encountered some unexpected results with the TelescopeAltAzToSky and SkyToTelescopeAltAz transformations, which led me to finding this thread about Nearest Math Plugin.

After your mention of looking for AltAz testers, I decided to switch the Math plugin to the SVD (Singular Value Decomposition) Math Plugin. This change resulted in the transformations aligning with my expectations.

Perhaps there might be a bug in the Nearest Math plugin? To provide more context, my use case involves a significant misalignment scenario. Specifically, I have adjusted my mount to have its hardstop pointing west, effectively rotating the mount by in azimuth 90 degrees. It's possible that this substantial misalignment might be contributing to the issues I observed.

Additionally, I noticed that the Inbuilt Math Plugin also struggles with accurate transformations under these conditions, so perhaps its a common failure mode, or the code isn't meant to address very large misalignments.

Let me know if there are any tests I can do to provide insight.

Read More...