04-21-2025, 07:45 PM
Hi Tom
The easiest way to measure your ie is to look at a sea horizon and correct for dip. You can use the 'D' setting on the coarse altitude control to check the 5 degree switch although I confess that I didn't bother! I was, though, very careful during the restoration process not to disturb the settings of the horizon and index mirrors. I average LOPs over my past 10 or so sights and compare to GPS to keep a running check on ie. One of my sextants had suffered damage to it's bubble mechanism, had a massive ie and drifts over time for some weeks after adjusting the index mirror screws although the other is very stable.
You will find your results improve significantly if you can get your averager (called 'automatic attachment', in the literature) to work. I was lucky in this respect - both of mine function without any help. If you have a look on e-bay for 'bubble sextant' you will find a seller called 'mark-ix-sextant' who sells a range of little information booklets that I have found very useful. I have 'Station Level Repairs' - tells you how to remove and replace the averager. 'Bubble Replacement and other Repairs' includes just about all the info I needed to get my sextants working and there is another called 'Civilian Maintenance Handbook' that gives details of the BM model averager mechanism - I don't have this yet!
You can always do manual averaging - just take a series of snap sights of your selected body, recording time and altitude, and average them with your calculator. This works well with a Link A12 sextant and a cheap plastic maritime sextant that I keep on my boat. I find 5 snap sights is generally enough.
Neil_s
The easiest way to measure your ie is to look at a sea horizon and correct for dip. You can use the 'D' setting on the coarse altitude control to check the 5 degree switch although I confess that I didn't bother! I was, though, very careful during the restoration process not to disturb the settings of the horizon and index mirrors. I average LOPs over my past 10 or so sights and compare to GPS to keep a running check on ie. One of my sextants had suffered damage to it's bubble mechanism, had a massive ie and drifts over time for some weeks after adjusting the index mirror screws although the other is very stable.
You will find your results improve significantly if you can get your averager (called 'automatic attachment', in the literature) to work. I was lucky in this respect - both of mine function without any help. If you have a look on e-bay for 'bubble sextant' you will find a seller called 'mark-ix-sextant' who sells a range of little information booklets that I have found very useful. I have 'Station Level Repairs' - tells you how to remove and replace the averager. 'Bubble Replacement and other Repairs' includes just about all the info I needed to get my sextants working and there is another called 'Civilian Maintenance Handbook' that gives details of the BM model averager mechanism - I don't have this yet!
You can always do manual averaging - just take a series of snap sights of your selected body, recording time and altitude, and average them with your calculator. This works well with a Link A12 sextant and a cheap plastic maritime sextant that I keep on my boat. I find 5 snap sights is generally enough.
Neil_s