NavList:

   

Reply

Thanks to Doug Royer for taking the trouble to explain in detail his
technique for horizontal sextant readings to measure distance off. I
intend to print it out and work through his example in the hopes of
better understanding it.

If I remember correctly the promise which led here was that horizontal
sextant readings would be more accurate than taking bearings with a hand
held compass, which is something I do a lot while cruising along the
coast. Typically the target, due to boat movement, swings from side to
side through the eyepiece and what I have to judge is the midpoint of
the average swings. I don�t expect that it is more accurate than to the
nearest few degrees but 3 of them typically yield a tight enough
triangle, often enough confirmed by GPS reading.

Sure a sextant can measure to less than one minute of arc but I�m not
sure how practical this would be on a small boat in average coastal
conditions;  about 1-2 metres of swell. I suspect Doug is talking from
the perspective of a big stable ship which could be quite different.

Still, its all useful grist to the mill of knowledge.  Contributions
like this are much appreciated and I wouldn�t, in his shoes, take too
seriously the occasional acerbic comments the list throws up.

   

Reply