NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Modifications to 2102-D
From: Brad Morris
Date: 2009 Aug 13, 14:15 -0400
From: Brad Morris
Date: 2009 Aug 13, 14:15 -0400
Hi Gary Yes, that is an approximation that can and does work. Off list, Chief Franklin recommended just the same thing. I felt that there was enough error to not make me happy. What I wanted was to have the sextant preset to nearly the correct value. Doing so eliminates (at least for me) the lack of certainty as to exactly which star is the right one and makes it easier to bring the star to the horizon. I assume the midpoint of twilight for time and go from there. The altitudes and azimuths are so close for the 15 minutes (or so at my latitude) as to not make a difference. To get the star in the view, yes, I use my Bygrave. Why? Because I can and it is fun! Nothing like the feel of that instrument in practice. Best Regards Brad -----Original Message----- From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of glapook@pacbell.net Sent: Thursday, August 13, 2009 1:12 PM To: NavList Subject: [NavList 9494] Re: Modifications to 2102-D Brad wrote: "I just use my to determine which stars would be practical. Since my latitude is 40 north, it places me right between the N35 and the N45 blue templates. Therefore, the altitudes and azimuths given really don't do the trick. " And: "Once I have the list, I swap over to the Bygrave to calculate the altitude and azimuth of each. That way, when I am ready to swing the arc, I can preset the sextant to the expected altitude and point via the compass. Generally, the star is right in the telescope! " A trick you can use to get better accuracy for latitudes between the template latitudes is to set LHA Aries (either using the almanac method or my modification or Chief Franklin's modification) and then take the template off the center pin and slide it north of south until the zenith is aligned with your DR latitude. This isn't perfect but will be accurate enough for you to be able to preset your sextant. gl "Confidentiality and Privilege Notice The information transmitted by this electronic mail (and any attachments) is being sent by or on behalf of Tactronics; it is intended for the exclusive use of the addressee named above and may constitute information that is privileged or confidential or otherwise legally exempt from disclosure. If you are not the addressee or an employee or agent responsible for delivering this message to same, you are not authorized to retain, read, copy or disseminate this electronic mail (or any attachments) or any part thereof. If you have received this electronic mail (and any attachments) in error, please call us immediately and send written confirmation that same has been deleted from your system. Thank you." --~--~---------~--~----~------------~-------~--~----~ NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---