A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Hewitt Schlereth
Date: 2011 May 14, 10:29 -0400
Oops, I was looking at my 1975 edition.
You are right. These are tables 24 and 25 - "Altitude Factors" and "Changes of Altitude in Given Time from Meridian Transit", respectively.
My Bowditch is 2002. Tables 29 and 30 in it are meterological tables: F to C conversions and direction/speed of true wind. Could you describe the tables you mean. I imagine they are "Altitude Factors" and "Change of Altitude in Given Time from Meridian Transit". Am I right?
Greg and Gary,
Thanks for your suggestions! I will definitely go better prepared in the future. Precomputation seems to be important part of preparation. I just threw the sextant, almanac, H.O. 229 and plotting sheets into the boat and went. Not good enough!
PatrickOn Fri, May 13, 2011 at 1:31 PM, Hewitt Schlereth <firstname.lastname@example.org> wrote:
Good Afternoon, Patrick -
Hey, you gave it the old try. There are calmer days ahead for Chesapeake Bay for sure.
Meanwhile, now that you're ashore, you could try reducing your noon sight using Bowditch tables 29 & 30 - the so-called ex-meridian tables. You may be pleasantly surprised.
For the queaze I found 25 mg of promethazine (Phenergan) effective. Read about it in Sailing Magazine back in the 70s where it said promethazine was used by NASA astronauts. As I recall NASA's dose was 50mg of promethazine with 25 of ephedrine. I found just half the amount of prometh and no eph did the trick for me.
HewittOn Fri, May 13, 2011 at 12:46 PM, Patrick Goold <email@example.com> wrote:
I found recently that there is one obstacle to using celestial navigation that is not mentioned in the books I have.
Early this week I was making a two-day jaunt across the Chesapeake Bay, the first of the season, on my 27 foot yawl, Restless. I hoped to get my first real sights taken from a small boat underway. There was a good chance that I would have a true horizon for noon sights and a good long fetch for morning and afternoon.
In the event I got a good feel for some of the practical difficulties of celestial navigation for an ordinary person on a small boat.
(1) cloud cover made morning and afternoon sights impossible on the first day.
(2) The first day noon sight had to be taken quickly through a small window in the clouds but several things made this difficult. (A) We were beating into a three foot chop that was very closely spaced. There was a vigorous pitch to the boat and we were heeling between 15 and 20 degrees. This made finding perpendicular, getting the sextant aligned with the eye and the sun so that there was an image in the mirror, and getting an accurate shot surprisingly difficult. All my land practice had not prepared me for this. (B) Nor had it prepared me for coping with the interference of the rigging and sails. It took me several tries to find a place on deck where the sail did not interfere with the reflected image. The shot I got was well past the estimated local noon and pretty unreliable anyway.
(3) When the cloud window closed and I put away my sextant, I had that slightly queasy feeling that signals the onset of seasickness. I could not make myself sit down at the nav station and work out even a simple noon sight.
(4) The next day the sky was clear all day. But now we were on a broad reach with a steep and substantial quartering swell. The boat was moving quickly through all six degrees of freedom. I am not especially prone to seasickness but this kind of tack is the one most likely to bring it on. Even if I have had a few days to get my sea legs (which I hadn't in this case), when the boat is yawing, swaying and surging in addition to pitching, rolling and heaving, I need to keep one eye on the horizon or go green. The sextant never left the case. Even had I taken a full set of sights, reducing and plotting them would have been beyond me.
These were not storm conditions. It was a rather typical spring day on the Chesapeake Bay. The wind was NE at 15 knots. The swell was no more than three or four feet but short and steep.