NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: My first Lunar
From: Jeremy C
Date: 2008 Jul 15, 22:32 EDT
Having a good DR position is convenient but not necessary when it comes to
clearing a lunar. Of course if you want to assess the accuracy of the sight,
then you want the actual position and correct GMT as nearly as possible. You
can figure out where you are, more or less, by trial and error from your
sight data. Go to the calculator on my web site, set the GMT of the sight to
22:19:30 and set your DR Lat to 14d 31'N and your DR Lon to 61d 38.1W. That
nearly matches your sights, lunar and altitudes, too. So assuming your
observations were good (and I would bet they were) you were probably about
30 miles west of Martinique. Does that fit your recollection?
Now as it happens, this is yet another one of this miraculous lunar sights
where you can do the clearing without using any spherical trig. If we take
the pre-cleared altitudes and distance (the altitudes of the objects'
centers and the center-to-center lunar distance) and add them up, we get
nearly 180 degrees. So adjust the Moon's altitude higher by about 24 minutes
of arc and then work it AS IF they were exactly opposite each other in the
sky.
Get the scoop on last night's hottest shows and the live music scene in your area - Check out TourTracker.com!
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From: Jeremy C
Date: 2008 Jul 15, 22:32 EDT
Frank wrote:
Having a good DR position is convenient but not necessary when it comes to
clearing a lunar. Of course if you want to assess the accuracy of the sight,
then you want the actual position and correct GMT as nearly as possible. You
can figure out where you are, more or less, by trial and error from your
sight data. Go to the calculator on my web site, set the GMT of the sight to
22:19:30 and set your DR Lat to 14d 31'N and your DR Lon to 61d 38.1W. That
nearly matches your sights, lunar and altitudes, too. So assuming your
observations were good (and I would bet they were) you were probably about
30 miles west of Martinique. Does that fit your recollection?
---------------------------------------------
Jeremy replies: I remember it being around there only because I was
sailing as a 3rd assistant engineer (read no real day to day knowledge of where
we were) on a training ship heading down the Caribbean. Given the date,
about 2 weeks into the voyage, I was only guessing at where we might be.
I do remember being surrounded by cadets looking at me strangely as they
collected their star sights as I was shooting lunars. None of them had the
first clue what I was doing, and frankly, neither did I. I also recall
taking about 40 minutes in my stateroom with Bruce Starke's tables to reduce
this one sight. I was able to cut that down with practice, but the
complexity of the tables soured me on lunars for many years. I will attach
the work form in a day or two.
I recognize that I could figure out about where I was by the altitude
observations, but here is a good exercise for an old-school lunar where position
and time are only approximate. I do have the actual UTC of the sight, but
I will reserve that knowledge for a few days to let the folks on the list play
with it.
-----------------------------------------------------------------------------
Frank continues:
Now as it happens, this is yet another one of this miraculous lunar sights
where you can do the clearing without using any spherical trig. If we take
the pre-cleared altitudes and distance (the altitudes of the objects'
centers and the center-to-center lunar distance) and add them up, we get
nearly 180 degrees. So adjust the Moon's altitude higher by about 24 minutes
of arc and then work it AS IF they were exactly opposite each other in the
sky.
-------------------------------------------
I am good with these miraculous Lunars no? LOL
Jeremy
Get the scoop on last night's hottest shows and the live music scene in your area - Check out TourTracker.com!
--~--~---------~--~----~------------~-------~--~----~
Navigation List archive: www.fer3.com/arc
To post, email NavList@fer3.com
To , email NavList-@fer3.com
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