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Frank,

Alex and I were and are trying to answer a few questions along the
lines of what you are asking.

By recording the type of sight, the conditions, the sextant and the
telescope power etc. and in a uniform manor we were hoping to quantify
the significance of some of these factors a little more. It was also
the basis of my appeal to the group to submit sights to be entered
into our spreadsheet some time ago to accomplish this.

With the 100 odd sights collected so far it is difficult to come up
with definitive statistics, however, a few comments (well adjusted
sextant, good IE, experienced observer etc. assumed) I would feel
comfortable making based on what we have so far are as follows

1.  I would stick by the within 0.2� limit using a good sextant on
land, standing up,  with a scope on the lower magnification side (in
my case 2X) and perfect observation conditions (i.e. not windy, clear
sky and nearly full moon).

2.  For the simple expediency of adding further stability to the
sextant by resting your elbows on your knees while crouching against a
rest you definitely get better results and I find I am closer to your
0.1� limit.

3.  If I move to the 12X scope, taking the sight standing is a bit of a
bear as the field of view is quite narrow and it is difficult to hold
still enough (at least for me!) to take full advantage of the extra
magnification so I am back to the 0.2� limit, maybe a bit better.

4.  I totally agree with the 0.1� error if I go with the 12X scope and
then somehow add more stability (i.e. lawn chair, elbows on knees
etc.).

5.  And most important when considering the above, you have to be
really really really careful about all those things Frank mentions
earlier in this thread!

6.       The optics I have for my Oaklet sextant are not top end
optics and I do believe that better optics although they may not
ultimately improve the accuracy, they would make getting the accuracy
you have easier.

I am going to keep adding sights to what I have so far and in
particular want to add more while out sailing. My sense of what I
might get under sailing conditions (42� sailboat, gentle sea, long
wave period) is that I might get pretty close to the 0.2� but we will
see. Obviously it will go to hell fast with a little chop.

As an aside I have taken lots of LOP�s while sailing and found in
excellent conditions (use your imagination) getting an LOP within 1�
is pretty reliable.


On May 30, 8:55�am, frankr...@HistoricalAtlas.net wrote:
> Jim, you wrote:
>
> "We used 5 sights and averaged the results. We found that we were
> within 0.2' �of the predicted lunar distance"
>
> So your results are about half as accurate as mine. At that level (0.1'
> versus 0.2') it's certainly not a big deal. You could apply observations
> with that accuracy to any... ahem... "practical" purpose , but do you
> have any idea what would make your observations more accurate? What power
> telescope do you use on your sextant?
>
> �-FER
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