NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Francis Upchurch
Date: 2016 Mar 18, 08:06 -0000
Thanks Greg,
Yes, I guess even 28˚ is too big for accurate kamal readings. I suppose the Arab/Indian traders were in lower latitudes.
Do you think they knew the declination of stars such as Canopus and could work out latitude from meridian passage measurement? How did you find the exact moment of the meridian passage?
Best wishes
Francis
From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Greg Rudzinski
Sent: 17 March 2016 17:04
To: francisupchurch@gmail.com
Subject: [NavList] Re: Metric Bookmark Kamal
Francis,
10' accuracy from the Canary Islands (Lat. 28° N) is very good using a kamal and Polaris. The kamal works best below 12° of altitude which limits the star choices at twilight. Night adapted eyes would probably get the job done. Moon light will work. I recommend using 56cm (22 inches) for string (dowel) length to allow for 1cm from the front of the eye to the center of the eye.
Greg Rudzinski
From: Francis Upchurch
Date: 2016 Mar 17, 07:46 -0700Great Kamal and results Greg,
I made a simple Kamal a la Burch a few years ago using a small plastic ruler marked in cms. With a string 57cm long, 1 cm =1°.
I only did a few latitudes with it, sun or polaris (when on holiday in the Canaries.Polaris. Hs too big in N Europe for a Kamal) and only got to within about 10' of correct Lat.
Does anyone know whether the Arab, Indian and Chinese sailors knew about Polaris correction and declination of the sun in order to work out latitude? I read somewhere that the Arabs, crossing the Indian ocean used different size strings for different ports of call.
Best wishes
Francis
