# NavList:

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

**Re: Noonsite using artificial horizon? Did I do it correctly?**

**From:**Bill B

**Date:**2014 Aug 28, 15:20 -0400

On 8/28/2014 3:46 AM, Samuel L wrote: > Does figure like 1.6' really mean 1' 12" ??? > > It's difficult figuring out the "tenths" of a minute using my calculator. > Let's start at the beginning, Babylonia and the sexagesimal system. Both time and degrees are base 60 systems. I'll let you Goggle that. There are 360 degrees in a circle (divisible by 6). There are 60 arc minutes in a degree, and 60 arc seconds in a minute. There a 24 hours in a day (divisible by 6), 60 minutes in an hour, and 60 seconds in a minute. To reiterate what others have said: Therefore 1/10 (0.1) of a degree, arc minute, hour of time, or minute of time is 6. (6/60 = 0.1 x 60.) 1/10 = 0.1 = 6 2/10 = 0.2 = 12 3/10 = 0.3 = 18 and so on. You many often find you have to make the conversion of tenths to minutes or seconds and vice versa in your head. Or you could make yourself a lookup table and package it with your calculator. Now on to the calculator: Different brands and models within a brand handle conversions in various ways. Like Ford and Chevy people, there are loyalties to particular brands and models within the discussion group. Anything you need to do can be accomplished with a $10-$15 scientific pocket calculator. Popular brands are Texas Instruments and Casio. Just read the instruction booklet and practice. I like my TI 30XA with three memory banks. Entering degrees, minutes and seconds is simple. For example, to enter 37d 46' 12" I enter 37.4612. Some members prefer an older solar Casio as they can enter tenths of a minute directly. Different (key)strokes for different folks. HERE IS THE IMPORTANT PART FOR MY TI (and most any low-end pocket calculator): Cel nav calculations are typically done with decimal degrees. A decimal degree is displayed as the degrees before the decimal point, and the minutes and seconds as a portion of a degree after the decimal point. 37d 46' 12" would be displayed as 37.77; 1d 30' would be 1.5d. At this point you may be thinking of throwing your hands in the air and wailing, "Barbie is right, math is hard. It hurts my brain." Don't despair. Read the manual on converting between decimal degrees and degrees, minute and seconds and practice. Enter in degrees, minutes and seconds and simple key press or two will convert degrees, arc minutes and arc seconds to decimal degrees. When you calculate your answer (which will most likely be displayed in decimal degrees) converting to degrees, minute and seconds is also a key press or two away. Easy peasy. Pretty much the same when working with time. Hope that helps.