NavList:

Dear Modris,

Thanks for posting all these interesting data. Many years ago Frank challeged all of us "to determine the arc error of a modern sextant by observations". Your data seem to meet the challenge.

I can share my own experience. (Many of my Lunar results were posted for this group about 20-25 years ago). I purchased my SNO-T on e-bay; it was made in 1990 (probably they discontinued their production in this year, I have never seen a later one). It came in factory wrapping, and I had no problems with it, except that the box was slightly damaged. The certificate showed +10" error everywhere on the arc, so I suppose that they simply did not do the testing, and the person who filled the certificate did not understand what s/he was doing:-)

Just for fun, I had it certified twice: by Cassens-Plath and Freiberger. Cassens-Plath issued their standard certificate only saying "Good for plactical purposes". Friberger prodiced an error table, where all values are less than 10", except the value at 120d which is 14"~0'2. 

I made hunderds of star-to-star and Lunar observations from my balcony, and I was unable to correlate my errors with the arc errors found by Freiberger. Most of my Lunar observations were within 0'2-0'3 from the true values (not taking arc error into account), which is about as good as your results.

To my surprise, I found that star-to-star distances were less accurate than Lunar observations. Probably this is because Lunar observations are made under the conditions when there is more light. About 1/2 of my Lunar observations were Sun-to-Moon, and they were the most accurate ones. And I also used only 7x inverting scope which I find by far superior to all other sextant scopes that I ever tried.

Alex.