Sun bearing table


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By pwb999 on 01/06/20 at 2:48pm (last edited 01/06/20 at 6:23pm)

Cumbria in common with the rest of GB has experienced an "unpredecented" period.

But this time of sunshine !!

This Spring's sunshine has recorded over 600 hours of sunshine with May being the driest for 124 years.

On my government sanctioned local walks the weather has given me time to reflect on how the ancients travelled so far and wide.

One tool was the simple observation of the Sun - Natures Compass.

A quick look at youtube will explain its movement and path across our skies.

Far better though is to simply place a stick in a sunny position and perhaps with a beer in hand simply observe its shadow. Mark it shadow's tip over a period of time and then work out for ourselves its pattern.

In short, the suns apparent travel is 15 degrees per hour from an Easterly to Westerly direction. (360 degrees divided by 24 hours = 15 degrees per hour). The bearing of sunrise and sunset varies according to the season.

Fortunately the sun always faces due South (180) at midday every single day of the year in our Northern hemisphere.

So its a simple task to subtract or add the hourly change of 15 from 180 to derive its true bearing.

In reality the Sun appears to move faster during the middle of day and slower at the beginning and the end of the day. Picture a walker tackling a similar ascent. They begin slowly at first tackling the increased gradient and then as it levels out they quicken their stride approaching the summit. Their descent is equally quick and then slows again with the increasing gradient.

Fortunately many internet sites publish the full tables detailing this unequal movement. It is then simple to compile a table. In this example I have extracted the 1st of the month details for Windermere. For ease of use, I have added a column for 10 and 30 minute intervals, with the hours being in BST.

I added a compass rose in degrees so that it was easy to find the reciprocal bearing of the sun or its shadow. The table may be simple but is accurate to a few degrees. It should be noted that more detailed tables are used by merchant mariners to check their ships compasses on a daily basis so the source data is very reliable.

With a bit of practice you can quickly orientate yourself using the sun or its shadow. For example on one of my low level walks, I knew the sun at that time was at 260 degrees. The path I needed was about 270 eyeballed from the grid lines on my A4 map. Turning on to the path the sun was now slightly to my left hand side. Coming to a gate I turned left and the path was now due South the sun now being on right, almost at right angles to my path. At a junction I had to head East and knowing that the reciprocal of 260 was 80 I used its shadow to steer slightly to the right. After a few walks it becomes very intuitive and you find you are actively trying to determine the direction of your shadow.

Plus its fun!

Give it a try and hope the sunshine continues...Keep Safe

Download the SunTable pdf file from here ...



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