NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Navy Mark V Sextant, Accuracy
From: Peter Henry
Date: 2004 Dec 23, 23:34 -0500
From: Peter Henry
Date: 2004 Dec 23, 23:34 -0500
I would like to receive some advice on two questions regarding the standard accuracy with this sextant. I have been using the instrument occasionally for approximately 1 year and learned to use a sextant from books. I have done calculations by hand but also with the computer program mac nav. I find that I get wildly varying accuracy from the most accurate of 1.5nm to 30nm approximately. I will also take multiple sites and have a varying range of 15 nm between the sites. I understand that the way to use this instrument is to center the bubble on the cross in the field of view and then to bring the object down to a point parallel to the horizontal line of the cross on either side of the bubble. Occasionally with stars I can bring it down centered in the bubble due to there small size. I also understand that the bubble should be twice as big as the object. Is this the right way to use this sextant? Secondly can a magnifying scope be added to this sextant to increase ones ability to precisely place the object on the horizon? What is the standard level of accuracy for this sextant? I also find that I must refill the bubble level every few months, that initially after filling the bubble I can change it's size up and down, but a few months out I can no longer reduce the bubble size. Obviously the bubble or one of the storage reservoir is leaking but I see no fluid though the sextant has a distinct smell which I assume is the fluid being turned into a gas. How do I find and fix this leak? Peter Henry