 Check out the bookstore at IRBS.com |
|
|
|
|||||
|
||||||
From: Bill (no email)
Date: Wed Jun 14 2006 - 02:03:55 EDT
Alex wrote:
> The suggestion that the arc is wrong near zero cannot be excluded,
> but then this is my second sextant with the same defect:-)
> Am I so unfortunate that all sextants I buy have bad arc near zero?
> :-)
Not likely ;-) If I recall from your beach shots with the SNO-T last year
there was an apparent systemic error. We talked about wave height at
Hunter's Pub. Maybe 2-3 feet? You initially claimed that was insignificant.
We worked out the dip, and tangent via distance vs. wave height, and it
about nulled out your error.
My impression at this stage of my development (outside of the problems
inherent in observing from a medium-displacement small craft, almanac
roundings, and blunders) is that accurate dip (both knowing your exact
height vs. the horizon and atmospheric anomalies) is the major stumbling
block to 0.2' to 0.4' accuracy.
I reference Frank's beach shots of Chicago from an Indiana shore, and our
inability to resolve the discrepancies. (Although, in my opinion not fully
pursued due to lack of list interest. I am excited about George's latest
find.)
Bill
|