Why is ROT_PA essentially the same as PA?

[Jesse Goldbaum]

Planewave alt-az telescope (latitude ~40 N) controlled by ACP. I'm new to ACP and alt-az mounts.

Looking at an image set starting at an altitude of 40, hitting 65 (at transit) and concluding at 53. At the beginning of the run both the PA and ROT_PA are 360. The PA slowly increases at 3 arcminutes per minute over the course of the run and... so does the the ROT_PA? The question is why isn't the "mechanical position" of the rotator rotating more significantly over the wide alt-az range, or why is it essentially the same as the PA? This is true in other runs when the PA isn't linear.

Off the top of my little head, I'd expect ROT_PA to be changing significantly while the PA is held constant.

To be fair, this isn't strictly an ACP question as I see the same effective keyword behavior in another alt-az Planewave controlled by NINA, though I didn't notice the issue then as the NINA controlled mount has significantly less overall drift.

Jesse