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Author Topic: Total Solar Eclipse  (Read 414 times)
harold
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« on: Aug 10, 2017, 09:42 PM »

Hello, my first pass, I'm still working on it, Harold.
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harold
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« Reply #1 on: Aug 10, 2017, 10:26 PM »

Hello, getting there, Harold.
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harold
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« Reply #2 on: Aug 11, 2017, 03:52 AM »

Hello, Here's my latest attempt, I'm still trying to figure out if the movement is West to East or East to West, it's making my brain hurt, Harold.
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harold
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« Reply #3 on: Aug 11, 2017, 09:43 AM »

Hello, looks like the movements are right, I added the Moon, Harold.
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harold
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« Reply #4 on: Aug 11, 2017, 12:11 PM »

Hello, the eclipse starts in the Pacific ocean and ends in the Atlantic ocean, I put in an end function to end the program, the eclipse in the upper right is at an angle so it wouldn't inter into the map, I think I'm done, Harold.
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harold
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« Reply #5 on: Aug 11, 2017, 08:34 PM »

Hello, I added U.T. and got a different Moon, Harold.
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harold
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« Reply #6 on: Aug 12, 2017, 11:27 AM »

Hello, I've added a simulated U.T. clock, Harold.
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harold
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« Reply #7 on: Aug 12, 2017, 05:34 PM »

Hello, I'm still playing with my eclipse program and the way I see it is that the Earth is rotating and South Carolina is moving to the East in front of the Moons' shadow at the rate of 1,035 mph (the Moons' shadow catches it as before), I have a program in mind to try to see if that is true, Harold.
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harold
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« Reply #8 on: Aug 12, 2017, 06:59 PM »

Hello, O.K., first pass, looks like I'm going to get it working the way I want it, I don't know if it proves anything, Harold.
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harold
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« Reply #9 on: Aug 12, 2017, 08:50 PM »

Hello, this is pretty much what I wanted, I'll be doing some more work on it, Harold.
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harold
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« Reply #10 on: Aug 12, 2017, 10:22 PM »

Hello, I described what I think will happen on August 21, Harold.
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harold
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« Reply #11 on: Aug 13, 2017, 10:20 AM »

Hello, I made some changes, I think that's it, Harold.
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Charlie
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« Reply #12 on: Aug 24, 2017, 07:51 AM »

Having gotten back from my eclipse trip, I have some time to comment on this eclipse program. I saw totality from a Burger King parking lot just off I-85 in the southern suburbs of Greenville, SC. It was a beautiful sight. It was my fifth, after Virginia Beach 1970, Prince Edward Island 1972, Gulf of California (Sea of Cortez) 1991, Aruba 1998.

The program gives a presntation that is a very good approximation to the actual event. Some things I noted, that make this particularly surprising (I guess that's the word to use):

The first thing I noticed about the program is that both the x and y coordinates are moving linearly with respect to time and therefore also with regard to each other.  

While this is approximately true on what is called the fundamental plane (a plane passing through the center of the earth and perpendicular to the shadow axis), the domelike nature of the earth's surface on the hemisphere facing the moon and sun prevents this from being the case on the surface of the earth.  It's also complicated by the fact that the offsetting nature of the earth's rotation, subtracting from the motion of the moon and its shadow, varies by latitude, and again by the domelike nature of the surface.

I've mentioned the domelike nature twice as it affects things in two ways:

Even without regard to the earth's rotation, the shadow axis is parallel to the surface and therefore moving more nearly perpendicularly to the surface, and therefore rapidly along the surface, the nearer to the endpoints of the overall path, while towards the center, the motion along the surface is slower.  

Taking the rotation into consideration, when, again at the beginning and end, the motion is more towards or away from the sun and moon, its component that available to offset part of the actual motion of the moon and its shadow is less.

I think one reason you were able to approximate this so successfully was that the U.S. is all near enough to the center of the eclipse path that these differences are minimal for this eclipse.

The second thing I noticed that the umbral shadow shown is a circle.  As the sun and moon are not directly overhead, the shadow axis is not perpendicular to the ground and therefore the umbral intersection with the surface is more like an ellipse with greater than zero eccentricity.

I've attached a NASA map showing the elliptical umbral shadows along the path of totality.  They are at regular intervals of 10 minutes, but as you can see, are not equidistant. Of course, these things are also dependent on map projection used, but I think the NASA map and the one you used are close enough to make the comparisons meaningful.

In the 1980's I had developed eclipse calculation programs, first for the Apple ][+, and then for IBM PC (i.e., MS-DOS), and for Commodore 64, based on Jean Meeus's books on the motions of sun and moon and how to use these for eclipses. While they are written in versions of Basic, I think I would find this overwhelming to port to Mintoris Basic, especially as I'm now more than 30 years older.

I'm trying to upload the NASA map file, but it seems too big. I'll try in another post later, after the time limit has expired. Or look up via its URL:

https://eclipse2017.nasa.gov/sites/default/files/publications/NASA_map_508.pdf
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harold
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« Reply #13 on: Aug 24, 2017, 12:22 PM »

Hello Charlie, thanks for your post, I enjoyed reading it, now I will study it, Harold.
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harold
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« Reply #14 on: Aug 26, 2017, 02:41 PM »

Hello Charlie, I've seen an Annular eclipse, but not a Total Eclipse, you must hold a record, 10-4 on all of the variables, you get into it a lot deeper than I do, I saw the map, good looking map, I jumped into computers with an IMSAI 8080 and North Star Basic, Harold.
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