NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Small zenith distance: a "bubble" sextant vs a Newtonian type sextant?
From: Tony Oz
Date: 2018 Feb 27, 06:13 -0800
From: Tony Oz
Date: 2018 Feb 27, 06:13 -0800
Hello.
Will a sight of a star near zenith taken with a bubble type sextant be more reliable than a sight of a star at medium/lower altitude taken with a Newtonian type sextant (referenced to the natural horizon)?
I think it should be the case because of the:
- more precise sextant positioning in vertical plane
- less or negligible refraction correction required
Been to Finnish Gulf this weekend, compared the height of a distant island/fort - in the quiet air and sunny conditions the refraction was very diffrerent to our usual conditions - I could measure the refraction to alter the height of the island as much as by 4' (four arc-minutes) in unfavourable weather. This time the fort at ~5km was in full view and the next one - in ~10km was clearly visible too.
Please comment.
Regards,
Tony
