NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Horizons and levels
From: Doug Royer
Date: 2003 Jul 15, 12:17 -0700
From: Doug Royer
Date: 2003 Jul 15, 12:17 -0700
Fred,let me explain all the variables in my statement.Useing both the liquid and glass horizons and both the M-25 and MS-733 sextants.Both types of horizons give me roughly the same results with both sextants.Useing the Davis I always,always,average the sights useing at least 3 cuts and times for each body.Doing so and painstakingly checking the sextant constantly for error during each round I can get on average about 0.2 of a mile from my known pos.Sometimes better,most times not.Useing the Tamaya and not averageing the cuts and times(as I do most times takeing sights at sea due to time or condition constraints)I on average get 0.2 mile from the known gps pos.However,useing the 733,if the sights are averaged as above I get a range from 0.2 mile to 40 ft. from the known gps pos.Most of the time between 0.1 and 0.2 mile.That's roughly a 500 to 1,000 statute ft. average useing the Tamaya. -----Original Message----- From: Fred Hebard [mailto:Fred@ACF.ORG] Sent: Tuesday, July 15, 2003 11:29 To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM Subject: Re: Horizons and levels Doug, I'm interested in how close you can get at home with the MS-733. Routinely 0.2' or is it closer? Thanks, Fred On Tuesday, Jul 15, 2003, at 14:11 US/Eastern, Royer, Doug wrote: > Just want to get a couple of more ideas before I leave.I also want to > explain what and why I did it.As for the 3 vs. 4 leveling bolts,maybe > 3 are > better or at least easier to use to level the reflective surface.It > takes > 45-90 sec. to level my horizon and can be frustrateing to get it > level.It > appears that with 3 bolts the leveling will be faster and just as > good.The > spirit levels I bought are round,the size of a 25 cent coin and have a > circle inscribed or printed on the convex plastic lens a little > smaller than > the size of a dime.They only cost $2.50 each,so they aren't very > accurate or > I should say they can't give that fine of a reading.However,the little > system that was made at least proves to me that this is a viable > alternative > to liquid levels.I leave it to you guys to hash out the finer details > of > makeing it more accurate.Once this thing,and the glass one I made, is > leveled(relative)I can view all bodies untill they move so much as to > need > to reposition the horizon.The Sun and Moon were observed.Last week I > observed the daytime Moon with the glass horizon I > made.Spica,Arcturus,Deneb,Altair,Vega and Antares were observed.Last > night I > observed Nunki(with the glass horizon and the MS- 733) untill the > light from > the riseing Moon washed it out.The question is how accurately must it > be > leveled?I started building a horizon because of frustrations useing a > Davis > horizon in strong winds during backpacking trips.I use a Davis M-25 > plastic > sextant on these trips and get an accuracy from the sextant as + - > 0.2' at > the very best.I'm just pleased as punch getting a fix within 0.5 mile > of the > gps pos. useing the above set-up.At home useing the above horizons and > the > MS-733 sextant I get finer results but that is to be expected.My main > goal > in this was to see if one can get good refections of stars or planets > with a > glass or plexiglas horizon,be fairly easy to use and be light in > wieght.At > least to me,these practical experiments prove it is all the above. > > ------------------------------------------------------------------------ Frederick V. Hebard, PhD Email: mailto:Fred@acf.org Staff Pathologist, Meadowview Research Farms Web: http://www.acf.org American Chestnut Foundation Phone: (276) 944-4631 14005 Glenbrook Ave. Fax: (276) 944-0934 Meadowview, VA 24361