NavList:

From: Gary LaPook <garylapook@pacbell.net>
Subject: [NavList] Re: Ix Diagram and Pub 208
To: NavList@fer3.com
Date: Tuesday, December 11, 2012, 1:57 PM

I like your diagram, it is pretty slick. I was trying to figure out how it works and I noticed that your "C" value is the product of sin LHA times cos dec. So this comes from the standard formula for azimuth, sin Z = cos LHA sin dec /cos Hc. You then rearrange this formula to  sin Z cos Hc = cos LHA sin dec. Using your diagram, moving from the outside scales to an intersection multiplies the two values so moving out to one scale from an intersection is the same as dividing. So after finding "C" (which is cos LHA sin dec and also sin Z cos Hc) starting with the value of "C" and the intersection with cos Hc and moving out to the azimuth scale your are actually dividing "C" by cos Hc and thereby  finding Z. The diagram could also be used for other trig problems involving multiplying and dividing sines and cosines. While trying some different examples, I discovered an interesting set of values to use. Let dec = 30, LHA = 40, Hc = 50 and then the Z  comes out to exactly 60. There must be some trig reason for this but I haven't figured out why. gl --- On Mon, 12/10/12, hanno ix <hannoix@att.net> wrote: From: hanno ix <hannoix@att.net> Subject: [NavList] Re: Ix Diagram and Pub 208 To: "NavList@fer3.com" <NavList@fer3.com> Date: Monday, December 10, 2012, 10:18 AM Thanks for,the kudos, Greg! In the meantime, I have developed a version that transforms the diagram into polar coordinates.  Perhaps that will be still easier to use? After Xmas I will send out more about that. Also, there is a novel sight-reduction-by-hand in the works. It works with a single 2-page table and covers angles from 0 to 90 degrees without special rules. The calculation uses only  integer numbers of just 4 digits. The error is +/- 1 sm throughout the full range of angles. The simple process will be contained on the worksheet. Sounds too good to be true? You guys will be the judges... Merry X-mas H From: Greg Rudzinski <gregrudzinski@yahoo.com> To: NavList@fer3.com Sent: Sunday, December 9, 2012 1:51 PM Subject: [NavList] Ix Diagram and Pub 208 Hanno Ix's rendition of the azimuth diagram has really delivered. After a plethora of trials it has proven remarkably fast and error free. I highly recommend it's use with Pub 208 or Weem's Line of Position in lieu of the Rust diagram. http://fer3.com/arc/m2.aspx/Azimuth-Diagram-example-use-HannoIx-oct-2012-g20982 Attached is an example of an octant bubble Sun observation sight reduction using Pub 208 and the Ix Diagram. The NA look-up and sight reduction fit easily on one side of an index card. Greg Rudzinski ---------------------------------------------------------------- NavList message boards and member settings: www.fer3.com/NavList Members may optionally receive posts by email. To cancel email delivery, send a message to NoMail[at]fer3.com ----------------------------------------------------------------