NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: What is a "Rare Brass List Compass& Clinometer,Deflector"
From: Joel Jacobs
Date: 2004 May 7, 15:53 -0400
From: Joel Jacobs
Date: 2004 May 7, 15:53 -0400
Brooke, That's an interesting item. I've never seen one like it before. I note the compass card at the bottom of the device, and the ruler-like upright scale. So here's a guess. When a ship assumes a list as a result of being out of trim, or in the case of a sailing vessel when it is heeled over underway, a different source of deviation is introduced due to the compass ridding at an angle from horizontal. I submitt that this device is used to measure this type of heeling compass error by simultaneously measuring the change in compass heading induced by the list, while at the same time measuring the amount of list that produced this change. There are certain compensating heeling magnets that hang in a tube directly beneath the compass card to adjust for this error. See Article 607 and the following, starting on page 88, of Bowditch. Mine is the 1995 Edition. Joel Jacobs ----- Original Message ----- From: Brooke Clarke To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM Sent: Friday, May 07, 2004 1:00 PM Subject: What is a "Rare Brass List Compass& Clinometer,Deflector" Hi: How is this used? eBay item 3721631458 http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=37967&item=3721631458 Thanks, Brooke Clarke, N6GCE http://www.PRC68.com
