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Gary,

The interest in your Bygrave project has been great and well
deserved.  But when talking about "backup" systems, I think about one
who is ill versed in CN, and just wants to make a safe landfall
without his failed GPS.  In this situation, I feel that using simple
noon sight procedures supplemented by sunrise/sunset longitudes, and
polaris Lats would be fine.  All that would be needed would be the
Nautical Almanac (for the Sunrise/ Sunset things) and would have the
included SR Tables for intermediate sights.  One might not prefer
these NA SR tables, but they DO work, and in a backup situation, why
be choosey?

Ken
On Mar 17, 2009, at 6:26 PM, glapook@PACBELL.NET wrote:

>
> I am real happy that I kicked off this topic and am impressed by the
> level of interest shown in using this simple to produce modification
> of the Bygrave for a backup celnav system. I am also impressed by the
> improved scales created by the other members on this list. A while ago
> I contacted Ken Gephart at Celestaire to get his opinion on whether he
> thought there would be any interest in a commercially produced version
> but he didn't think there would be. He thought that a simpler system
> would be better considering the lack of celestial training of your
> everyday sailor. I started this discussion stating that it was meant
> for those knowledgeable in CELNAV, the virtue of this system being its
> compact size and its low cost. He said that if they already had the
> Nautical Almanac they had the reduction tables already published in
> the N.A. (I, for one, really dislike those tables, your mileage may
> vary.) Work out an example with the N.A tables and compare the work
> with the came computation with the Bygrave and I think you will agree
> the Bygrave is easier to use. Those same non celnav sailors wouldn't
> be expected to buy an N.A. every year either so another advantage of
> this system is the long term almanac.
>
> So Ken, any more thoughts about this considering the great interest
> shown on this list?
>
> gl
>
>
> On Mar 17, 1:09 pm,  wrote:
>> I am another long time lurker, who got all excited about Gary
>> LaPook's flat Bygrave scales, and also got cracking on my own
>> version of scales. Unfortunately it took me a while to complete
>> due to distractions like family and job. So Dave beat me to it by
>> a month or so.
>>
>> In any case I decided to publish my version of scales as well. Not
>> because they are better than Dave's, but because they are written
>> in Postscript, and can be easily customized by each individual
>> user. It's easy to change width of scales to the size of your
>> sheet or cylinder, number of lines, font size, frequency and
>> thickness of tickmarks etc.
>>
>> The files cot.ps and cos.ps can be edited with text editor like
>> notepad, and then converted to PDF using free Ghostview tool. To
>> do that you also need to install Ghostscript. Here are links to
>> download page.
>>
>> http://pages.cs.wisc.edu/~ghost/doc/GPL/gpl863.htmhttp://
>> pages.cs.wisc.edu/~ghost/gsview/get49.htm
>>
>> You could even easily define other scales using this template e.g.
>> sec()/csc() for Ageton method like Andrew suggested in one of the
>> previous posts. Though this would require to write up the function
>> in Postscript stack based form using just (sin, cos, and atan) as
>> these are only available trigonometric functions in postscript. I
>> would be glad to help, if somebody decides to do that.
>>
>> Note that common procedures for drawing the scale are in scale.inc
>> file and it must be in the current directory when opening .ps
>> files with ghostview.
>>
>> And I must also repeat Gary's warning, when printing PDF files
>> make sure to set Page Scaling to None. I wasted few transparent
>> sheets before figuring that out.
>>
>> Martin
>>
>>  cos.ps
>> 1KViewDownload
>>
>>  cot.ps
>> 2KViewDownload
>>
>>  scale.inc
>> 2KViewDownload
>>
>>  cos.pdf
>> 23KViewDownload
>>
>>  cot.pdf
>> 85KViewDownload
> >


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