NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: New compact backup CELNAV system RENAMED Accuracy of Bygrave Slide Rule
From: Brad Morris
Date: 2009 Apr 15, 09:38 -0400
From: Brad Morris
Date: 2009 Apr 15, 09:38 -0400
Hi Frank Quite the contrary. I am not advocating the exclusive use of HO229. That is the reason I have the MHR-1, because there is more than one way to skin a cat. How you get the solution to the celestial triangle is up to the preference of the user. One further misconception is that you need all 6 volumes in order to use HO229. That's when you get to large mass and volume. One of the reasons that you see single volumes (and not the set) on eBay is just that. As a practical matter, you need one, perhaps two volumes to navigate within your area. Why carry volume 6 (75 degrees to 90 degrees) unless you plan on navigating there? When they get done with the volumes they have, they sell them just as they have them, partial sets. Being the polar nut, I went after all 6 volumes. They take about 12-14 inches and weight about 8-10 pounds (estimates!) I will state again that I am not opposed to the Flat Bygrave, at all. It puts a very useful tool well within the (financial) grasp of every navigator. The Cylindrical Bygraves are expensive and sought after by many other than navigators, pushing them out of the reach of many. Gary has found a way for everyone of us to enjoy this solution. I was merely investigating solution provided, as an engineer. We question everything, not because we think it is bad, rather to probe the design to make it better. Please don't misunderstand my method! Best Regards Brad -----Original Message----- From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of frankreed@HistoricalAtlas.com Sent: Wednesday, April 15, 2009 1:10 AM To: NavList@fer3.com Subject: [NavList 7949] Re: New compact backup CELNAV system RENAMED Accuracy of Bygrave Slide Rule Brad, you wrote: "There is a bit of a conundrum here. The amount of work needed to extract a value from a set of tables varies little, except if you are using Sumner Line of Position or earlier. There will be some quibbling about the arrangement of the tables being "inconvenient" in HO229 or that there is no interpolation required of HO249, but at the end of the day, you have spent just a few minutes in the tables themselves. Why not get the maximum resolution that you can?" If I understand you correctly (and please correct me if I haven't), you're asking why someone would prefer one of these compact slide rule-style methods of reducing sights considering that they have slightly reduced accuracy in some cases when the amount of work is the same. So why not just bring along HO229 then? There are a number of answers to this that I can think of. Here's a couple... First of all, this isn't just a theoretical game (not to state the obvious!). If someone has an intention to do celestial today, very practical considerations come into play. Real navigation is done by GPS, and for that you should cut no corners: carry spare hand-held GPS receivers, bring lots of batteries, etc. Since you don't really "need" celestial, when the time comes to consider what to pack on your "three hour tour" or "three week adventure" the bulk of those big tables could be a serious deterrent. Do we bring the cooler full of sandwiches or do we bring HO229? So "these days" I think there are real benefits in going light (in terms of weight) and Gary's rather cool method is certainly light. The modest reduction in accuracy that may result is probably not important considering how far it is from the accuracy of GPS already. Second, since celestial is very much a secondary, even tertiary, method of navigation in this day and age, the choices people make for using certain types of sight reduction is much more a matter of personal interest than absolute accuracy. I suspect that a lot of navigation enthusiasts who cut their teeth on HO229 would find great pleasure in using one of these slide rule-like methods. If for no other reason, then because it makes something old and routine, new and interesting again. -FER "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." --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---