NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: NA daily pages, moon
From: Scott Owen
Date: 2008 Oct 30, 21:27 -0500
From: Scott Owen
Date: 2008 Oct 30, 21:27 -0500
frankreed@HistoricalAtlas.net wrote: > But I think there's general agreement that > the data in that little moon box have very limited navigational value. For > another example, why do we need to know the moon's percent illumination (to > the nearest percent)? The percent illumination was added in the 1980s. Why > wasn't the small phase diagram sufficient? > > -FER Frank, Does it have any value for lunars or celnav? MAYBE. However, it does have value depending on HOW/WHERE you do your navigating... say flying from a ship at night. The moon's percent illumination is given to the nearest percent because Naval Aviators use percent moon illumination for maximum moon illumination requirements for flying at night using night vision devices [NVDs]. That is, if the moon illumination is too bright you can NOT use NVDs because of NOT being able to see the cockpit instrument panel while flying on NVDs. IIRC, the requirement was to the nearest percent and not the nearest 5 or 10 percent. FWIW, I used NVDs in the cockpit back in the 1980s and 1990s. Of course, there may be other uses for percent moon illumination, I just know what I used it for 10-20 years ago and is still used today wherever NVDs and flying at night from a ship come together. As to the value of percent illumination to lunars or celnav... well, if you hooked up a 5th generation NVD to a sextant... there actually might be some nights when you couldn't effectively use the Sextant/NVD combination. At some percent moon illumination it would be too bright to use the NVD for celestial shots. The navigator [once the max moon illumination is known] might want to change to a different optical device before sunset using a quick glance at the NA. I am sure that Lu thinks this explanation is BS too. He is of course entitled to his opinion. --Scott --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---