NavList:

   

Reply

Hi George, you wrote:
"What Frank Reed has written below is all very well, but has little to do with 
the question being asked, which was about deficiencies in a particular full 
formal clearing procedure, not some shortcut."

I posted those four items, following up on your post, in order to clarify that 
there are a number of distinct things going on with lunars close to 90 
degrees. Point TWO applies only to series methods (which is just what I 
said). Point FOUR I described as being "almost certainly not relevant 
historically". But the other two points apply to all lunars. To reiterate on 
point ONE, lunars around 90 degrees were simply popular in practice for a 
variety of practical reasons. To reiterate on point THREE, lunars around 90 
degrees are insensitive to errors, even very large errors, in the Moon's 
altitude, and this may also have contributed to the popularity of lunars 
around 90 degrees. Note that point three applies to all methods of clearing 
lunars, including Dunthorne's and anybody else's. Any of these factors, but 
especially the latter two, might have led an author to mistakenly think that 
there was something special about lunars near 90 degrees in a particular 
clearing method. But as I have already said, the author who wrote this up in 
the "Lehrbuch der Navigation" was simply mistaken. It's not true that 
Dunthorne's method has any significant inaccuracy for lunar angles more than 
20 degrees away from 90 degrees (though a case can be made that it is 
inaccurate for lunars close to zero).

-FER



--~--~---------~--~----~------------~-------~--~----~
Navigation List archive: www.fer3.com/arc
To post, email NavList@fer3.com
To , email NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---

   

Reply