NavList:

Sean,

Those appear to be excellent lunar observations. Only the first one is a bit wild. The rest are right on the line. If we had some reason to ignore the first one, the mean and standard deviation for the rest are both 0.1 minutes of arc --about as good as it gets! What instrument and what scope magnification, if I may ask?

Can we legitimately exclude that first observation? If we use an outlier scheme, placing an error band with the right slope and a width of 4 s.d. (with some s.d. based on prior experience, reasonably 0.25 minutes of arc), then all of the observations fall within the error band except the first which is clearly outside. So that works, and it's an a priori scheme for excluding outliers. You average the rest and get 0.1' error. Really excellent. You could also consider the method proposed in the Ocean Navigator article which Gary L. posted last month: take the median observation from the set and ignore the rest. The median case here is 0.2' out so this would also count as "really excellent". And this, too, is a legitimate a priori method for managing outliers.

In your graph, I don't understand what the dashed line represents, and I don't understand the points you've marked with squares and keyed as calculated distances. How were these calculated? Incidentally, when I first skimmed your post mentioning Mars and saw you used 'easy lunars' for one pass through the calculation, I immediately worried that you might have missed the large parallax of Mars right now, but kudos, you got it. 

Thanks for posting your observations. I was looking at Mars and the Moon last night and wishing I had a little more time to spend to take some myself. As far as I can remember, I haven't shot any Mars lunars in over ten years! Maybe tonight...

Frank Reed
Clockwork Mapping / ReedNavigation.com
Conanicut Island USA