For anyone looking for more resources ahead of the April 8, 2024, eclipse (especially Wolfram Language resources for computing and analyzing eclipses), check out Stephen Wolfram's new book "Predicting the Eclipse: A Multimillennium Tale of Computation". You get a copy on Amazon: https://www.amazon.com/Predicting-Eclipse-Multimillennium-Tale-Computation/dp/1579550878

I mention all of you and your ideas in this blog: Solar Eclipses from Past to Future, Earth to Jupiter. Thanks for wonderful contributions and fun!

To highlight the diversity of the discussion we can use new in Wolfram Language function WordCloud:

post = Import["http://community.wolfram.com/groups/-/m/t/463721"];
Row[{
  WordCloud[ToUpperCase[DeleteStopwords[post]],
   ColorFunction -> "RustTones", Background -> Black, 
   ScalingFunctions -> (#^.1 &)],
  WordCloud[ToUpperCase[DeleteStopwords[post]],
   ColorFunction -> "RedBlueTones", ScalingFunctions -> (#^.1 &),
   Background -> ColorData["RedBlueTones"][0], 
   WordOrientation -> {{0, \[Pi]/2}}]}]

In the code above there are three handy tricks. First is that option WordOrientation has diverse settings for words' directions. Second is that a good choice ScalingFunctions can grant a good visual a peal, and simple power low I've chosen is often more flexible than logarithmic one. The third trick is subtler. It is the choice of background color to be the "bottom" color of the used ColorFunction. Then not only sizes of the words stress their weights, but also fading out into the background.

Hi Marco,

inspired by your and Sander's posts on how much the sun was covered during the last eclipse, I also tried to write an evaluation from picture data. For this I use Tanvi's first picture (@Tanvi: Thanks for posting!), because in the second one the sun seem to be "cut" a bit at the edges by clouds. My ansatz is to use a model of the eclipse consisting of two equal sized disks overlapping each other. This simple model has five parameters (the number on the right side represents a fitness of match):

One can define a "fitness function" to quantify the goodness of match and try an optimization for this. Unfortunately I was not able to get that working perfectly - the result of NMaximize is not bad but by no means perfect. This seems strange because it is very easy to improve the solution by hand.

Once a result is obtained, e.g.:

one can very easy calculate the covering:

\[ScriptCapitalR] =  RegionDifference[Disk[{x, y}, r], Disk[{x + dr Cos[\[Phi]], y + dr Sin[\[Phi]]}, r]] /. opt;
Print["covering: ", 100 (1 - RegionMeasure[\[ScriptCapitalR]]/(Pi r^2) /. opt), "%"]

Otherwise I would not have a quick idea on how to do that - probably some ugly integrals ...

I have attached the notebook with the code. The next solar eclipse may come!

Henrik

Attachments:

Hi Tanvi and Vitaliy,

I know that this does not work quite well yet, but if I take the photo that Tanvi posted

img = Import["~/Desktop/Eclipse.jpg"]

and crop it a bit:

img2 = ImageTrim[img, {{447.386`, 409.278`}, {513.381`, 344.818`}}]

I get:

The question that also relates to Sander's question in Vitaliy's post is: how much of the sun was covered. The idea is to cover the crescent by a disk:

MorphologicalComponents[Binarize[img2, 0.4], Method -> "BoundingDisk"] // Colorize

then determine the shape of the crescent itself:

MorphologicalComponents[Binarize[img2, 0.4]] // Colorize

and then calculate the respective areas:

full = ComponentMeasurements[MorphologicalComponents[Binarize[img2, 0.4], Method -> "BoundingDisk"], "Area"][[1, 2]]
(*1206.5*)
crescent = ComponentMeasurements[MorphologicalComponents[Binarize[img2, 0.4]] // Colorize, "Area"][[1, 2]]
(*311.75*)

The ratio of which is:

crescent/full

This gives a covering of about $74\%$. This number is only a rough estimate. The fitted disk is not quite right as you can see in this plot:

ImageMultiply[img2, ColorNegate@(MorphologicalPerimeter[MorphologicalComponents[Binarize[img2, 0.4], Method -> "BoundingDisk"], 0.2] // Colorize)]

The black circle is the estimate of the shape of the full sun, which is obviously not quite what we want.

Cheers,

M.

PS: Tanvi, thanks a lot for posting the photos!

Thanks you for a very interesting analysis, professor Thiel. Here are a few pictures of the eclipse from Aberdeen, around 9:25 am.

Thanks Dr. Kaurov, I took the photos on an iPad, there's no processing done on the pictures.