NavList:

Thanks for the response, there is no obvious play in the micrometer knob. All the screws are tight. I took off the cover on the micrometer knob and tightened the scew that attaches it to the gear shaft as much as I was comfortable with (it bears down on plastic in the knob). I even tried pressing with a finger agains the gear to press it more firmly into the rack while turning the micrometer both ways - still the same amount of backlash. I did the same with pressing against the end load spring while checking for backlash - same result. The micrometer feels like the same resistance the first 2 minutes as the rest, although the micrometer seems to have a bit more resistance in one direction that the other - mostly around 0 degrees. I even measured some star distances so I wasn't just checking backlash at near 0 degrees, same results. I think what I need to do is just appreciate that I can get good readings with careful operation of the sextant and try to understand that there are some things I just don't understand (like where this backlash is coming from).

Thanks,

Doug