I have recently been investigating the different models specifically with regards to the horizon. It seems to be a very significant place for a number of reasons.
I looked for data describing the horizon in mathematical terms but could not find any.
If you know of any source providing data like
1. height of observer vs
2. distance to horizon vs
3. horizon declination angle
please let me know asap.
I eventually plotted the light function according to this manual and adjusted it for each model.
The light paths were programmed into a publically available program called Photon. I took permission by the owner of the code to customize it and make it publically available so here it is Photon-Bowditch. It is straightforward to use. (The horizon is always at x=0).
Please note, that you can plot this light function on Desmos.com First make sure you change to Degrees from the graph settings at the top right corner. Once you plot the graph make sure you scroll out with your mouse quite a bit until the earth is in view (6x10^6 must be in view on each axis).
1. Draw the earth by entering 'r=6371000' in the equation field.
2. Draw the convex light path 'r=6371000+(((((90-\theta )/360)*((2*\pi *6371)/(1.852*1.169)))^2)*0.3048)'
3. Draw the concave light path 'r=6371000-(((((90-\theta )/360)*((2*\pi *6371)/(1.852*1.169)))^2)*0.3048)'
Unfortunately I cannot plot the FET light function on Desmos.
I will update this thread on the subject at hand as new info becomes available.
For people knowledgeable in atmospheric refraction and bending of light, can you please comment on the charts provided in Photon? Do they seem trivial or do they seem substantial with regards to how you envision light bending in the concave earth?
When I started my one month investigation into lighthouses, I never thought this would develop into such an exciting subject.
I was astonished to not find ANYTHING online regarding horizon declination angles so I had to guess. LOL
Simply amazing stuff Steve and thanks for taking the time.
I am sure we will derive a lot of useful information because of your measurements.
I am also thinking of getting a friend of mine with his theodolite and run sun measurements from every place possible. In Cyprus we can go to any elevation in 1 day... from beach to mountain.
If you have some requests, let me know and I will arrange it soon.
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