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Dear David,

Thanks for the comment.

Having the Newtonian+NH (the Natural Horizon) as the golden standard, where ANY movement however minuscule does not affect the apparent position of the horizon and the star, I want the similar behavior from an AH sextant.

I think is is most difficult to achieve with bubble AH because its' responsiveness massively depends on the bubble size. The bigger the bubble - the more responsive and accurate it is. But this big and accurate bubble is difficult to align with a star - no apparent center to watch for. The bubble small enough to be convenient with a star is far too sticky...

I'm following an attempt to create a bubble AH for a "classic" sextant, the experimenter had to attach a cell-phone's vibro motor to make small bubbles respond to the gravity better.

I wonder if a gyro AH is free from "unresponsiveness".

Warm regards,
Tony
60°N 30°E