NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: New compact backup CELNAV system
From: Gary LaPook
Date: 2009 Mar 17, 16:26 -0700
From: Gary LaPook
Date: 2009 Mar 17, 16:26 -0700
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 --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---