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moon exempt from eq mount PA tracking?

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The moon moves at a different rate and follows a different path to the ecliptic. So tracking will always be a pain.

Suspect that some systems may supply a lunar rate but no many. Just accept that you have some tracking but not accurate tracking, it won't disappear quite as fast as it may otherwise.

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Most mounts that track will have several rates programmed into them. Sidereal is the 24 hrs per rotation that compensates for Earth's rotation - this is the rise/set that we see with all stars and distant objects. Lunar rate compensates for the fact that the Moon rotates eastward around the Earth every 27.3 days. This rate is really very little different from true sidereal rate - and for visual work it makes little difference. Most modern GOTO scopes automatically adjust the rate when you select an object to view from the controller.

There is also King rate - this compensates for the refractive effect that occurs when tracking an object very close to the horizon. I suppose this might be effective for viewing Mercury or Venus, but I've never used it at all.

Hope that helps!


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The moon doesn't deviate hugely from sidereal rate for the purposes of casual visual observation or webcamming. It will take over an hour to drift by its own diameter on a sidereal tracking mount. Personally I have never bothered to switch to lunar rate because the deviation from sidereal has never affected me, though I can't claim to be any kind of lunar specialist.


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