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    Re: New compact backup CELNAV system RENAMED Accuracy of Bygrave Slide Rule
    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
    -----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 
    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.
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