A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Jeremy C
Date: 2015 Dec 27, 09:04 -0800
The only advantage that I see of using a whole horizon mirror in conjuntion with a 7x scope is being able to use the double prism filter found on some sextants like the Cassen's and Plath Horizon Ultra. Since the prism can only be used with a whole horizon mirror, it is a necessary feature. Other than this, a split mirror with the 7x scope gives the advantages of better light transmission along with the apparent whole horizon view which I find easier to use from the deck of a ship.
Of course if you are swapping scopes on a regular basis, you will lose the whole horizon view, so maybe you want that whole horizon mirror on there for low magnification work. I think the selection of features depends greatly on what you are shooting and from what platform. I don't think that there is a universal configuration for sextants which is why I chose a sextant that gave me numerous options.