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Bruce

There shouldn't be any backlash with an A10, as it is provided with a
backlash spring. The index bearing after 60-odd years is often in need
of lubrication to ensure free movement (I once had one completely
seized). The bearing can be difficult to pull apart and reassembling
with the anti-backlash spring correctly tensioned can be a trying
exercise. You can probably improve the index error by setting the
instrument to a sea horizon, removing the read-out counter, setting it
to zero (allowing for dip) and replacing.

I will be covering these and other details in an e-book on A10
restoration, due out at the end of February. It will be along the
lines of my e-books on the reconditioning of the Mark IX series bubble
sextant and my "Naked Nautical Sextant". See www.sextantbook.com for
details. Meanwhile, you can contact me off line about your A10 if you
wish.

Bill Morris

On Nov 28, 4:08�pm, bruce hamilton  wrote:
> All times GMT 27 Nov 2008
>
> A-10 Sextant with 31.5' index error off the arc (horizon reading is lees
> than zero in case if am mixed up)
> Sextant has no other calibration. I frequently get LOP's within 2 miles
> of my AP so I am happy. It has backlash so I try not to change
> directions. �I suspect some other error as stars with higher altitudes
> tend to give me bigger errors.
> I am actually quite surprised that I am getting a fix that is close
> enough to find the airport (or Bermuda) if I had do. I have an A-12 and
> Mark IX, but I only drag out one an evening.
>
> Thanks
>
> I am presently using CelestNav 3.0 for the palm pilot to work out the
> sites. I would appreciate any comments on the program. I like it for
> everything but the fix calculation, but I think 3.0 is only a Beta.
>
> AP 49d �16.1 N �123d 7.1 W
>
> Pollux � 06:19:33 � 27d �59.3'
> Vega � �06:16:31 � 13d � �0.3'
> Betelg � 06:10:53 � 28d �44.3'
> Altair � �03:56:11 � 22d �37.0'
> Vega � �03:54:45 � 32d �06.9
> Capella 03:52:46 � 39d �35.7'
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