On July 7th we took a trip to the beach and I was able to use the natural horizon on Lake Michigan for a series of afternoon sun sights. This is the first time I've been able to use other than an artificial horizon or a bubble sextant. It was exciting to actually try it at last. I used a Davis Mark 3.
Good fun and the results were interesting.
I varied between upper and lower limb sightings, took six different sightings with multiple individual sights for each one. I threw out the sixth set of numbers because they were all over the place. They were taken in a rush and by then I was hot and tired.
The other five sets however I was able to work up. I had three sets that were basically the same, though the LOPs were all out about 8 nm to the west of my actual position. One set was dead on and a fifth set was about 10 nm east.
UL and LL didn't appear to make any difference, the set of three sights contained both.
I adjusted the mirror between each set of sights. I had only the horizon for this which I wasn't used to. When practicing at home I use a distant tree which I'm able to use to correct both horizontally and vertically. With the horizon all I could do was get things lined up one way and turn the sextant on its side to adjust the other way which is far more difficult. I'm assuming the errors were a combination of how my eye perceived the horizon and not getting the index correction quite right.
Hopefully I'll get another opportunity soon and can work on my technique more. Possibly I can nail down that elusive IC for this sextant.
Good fun and the results were interesting.
I varied between upper and lower limb sightings, took six different sightings with multiple individual sights for each one. I threw out the sixth set of numbers because they were all over the place. They were taken in a rush and by then I was hot and tired.
The other five sets however I was able to work up. I had three sets that were basically the same, though the LOPs were all out about 8 nm to the west of my actual position. One set was dead on and a fifth set was about 10 nm east.
UL and LL didn't appear to make any difference, the set of three sights contained both.
I adjusted the mirror between each set of sights. I had only the horizon for this which I wasn't used to. When practicing at home I use a distant tree which I'm able to use to correct both horizontally and vertically. With the horizon all I could do was get things lined up one way and turn the sextant on its side to adjust the other way which is far more difficult. I'm assuming the errors were a combination of how my eye perceived the horizon and not getting the index correction quite right.
Hopefully I'll get another opportunity soon and can work on my technique more. Possibly I can nail down that elusive IC for this sextant.
I used to be a normal person, then I discovered how to locate myself on this planet using a star.