# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Lunar Calculation Presentation
From: Jim Hickey
Date: 2022 Sep 2, 12:05 -0700

So Jim's two cents worth.

Over the years I have often been asked by curious onlooker as I was taking a sighting at the beach "what are you doing" or "how does that work'" and I have always been disapointed with how I handled the question. For those of us in a technical field or, in this case, functional knowlege of the subject, you tend to lose the questioner with too much detail becasue our minds explode with so many thougts and details. You can only cram so much information into limited time. The baud rate ain't high enough.

I actually got annoyed enough with my ineffective answers and devised an "elevator speech" on the key points of standard celestial navigation going from angle as a distance using the flagploe analogy to the GP concept to circles of position which gets you the base concepts which is about as far as most want to go. Annex the rest to "there's a bunch of corrections and stuff to consider but that's bascially how it works". It's also reasonable that a reasonably curious person might even retain that information. Talking about refraction, parallax and assumed positon etc. just becomes obstrification for the modestly interested. If they are really interested, they are on the hook and will look for more.

I view the approach to lunars as similar. You have a table or almancac that lists the time of a certain angular distance between the moon and another celestial body. Measure tha ngle and you have the time. Done. The heavy lift is really in the clearing which is all about those infernal corrections which requires all that math stuff but in the end, it really is as simple as "if the angle in the lunar distance table is 40 degrees at 3 am and 40 degrees 30 minutes at 4 am and you measure the distance at 40 degrees 15 minutes, you can readily calculate the time to be 3:30 am.

I have taught the Power Squadron celestial nav course over the years and continually find that there was so much time spent on correcttions and tables that often the fundamental basis of what was being done was often lost. Better to start on a very sound fundamental base and develop from there.

If the keeners in the class want more, there is plenty of excellent infromation to have at hand should they ask.

And I try and keep that "note to self" handy. "People really don't like trig and calculators and tables and logs like I do!".

Anyway, just a couple of thoughts. Hope it helps.

Jim

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