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# Watching the Solar Eclipse Safely using SOLIDWORKS

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If you watched the 2017 Solar Eclipse yesterday, and are reading this, then you likely watched it safely. In the days leading to the eclipse, I was running around (like all good procrastinators) trying to find proper safety glasses. Well, guess what? They were sold out… EVERYWHERE!

Not to be deterred, I got to googling and found an easy, and free way to make a pinhole camera out of a cereal box. But if you follow my blogs, you know that’s not enough for me. I had to see what I could do in SOLIDWORKS.

SOLIDWORKS has a model size limit of 1km3, so modeling the whole solar system at 1:1 scale was out of the question. In fact, even scaling it would be difficult since the vast aspect ratios go beyond 8 decimal places. I remember reading somewhere that the relative size of the sun (and moon) to your eye here on earth is about the size of the hole in a piece of notebook paper. So I got to math-ing. Yeah, that’s a word now…

I started with calculating the angular diameter of the sun from here on earth.

The angular diameter of a circle whose plane is perpendicular to the displacement vector between the point of view and the center of said circle can be calculated using the formula. (Wikipedia)

Where d= the sun diameter and D= distance to the sun.

I love Wolfram Alpha…

Next, I know the length of the average human arm is about 25” (635mm) [www.reference.com]. I add about 3” for the distance from your shoulder to your eyeball. It ends up being about 711mm.

With those numbers, we go to SOLIDWORKS.

I made a sketch starting at the origin (focal point) of an angle of 0.00933… radians about a centerline that was ~711mm long. This gives me a relative diameter of ~6.6mm. This sketch represents the light rays coming off the sun, starting from what the sun looks like at about an arm’s length away. As mentioned above, we are shooting for roughly the size of a 3-hole punch. The calculations came to about 6.6mm, the paper I had measured at about 6.8mm. Not bad considering all the rounding we have been doing.

The thumbtack I used to poke the hole was 1.2mm in diameter, but where do I put that? Not at the focal point. SOLIDWORKS to the rescue again! I started a 3D sketch and drew a circle with the correct diameter. By adding a couple sketch relations to the light rays, the hole placed itself.

Next I created the cereal box around the hole’s location. Also, I added a cut for the viewing port.

Now for the fun part. Using SOLIDWORKS Visualize, my colleague, Jesse Sprague, added a light at the end of the sketch line and turned off all the other lights. Since Visualize uses advanced ray tracing technology, we are able to accurately simulate what we saw yesterday! This is a rendering looking into the viewing port (the virtual sun is behind us).

While a still image is pretty cool, I asked Jesse to take it up a notch. I made an assembly in SOLIDWORKS of the moon crossing into the sun’s path. Using a path mate and the SOLIDWORKS Motion manager, this was a snap. And before anyone starts freaking out… the path is approximate for Rochester, NY. I eyeballed it based on this site.

Here is the SOLIDWORKS Visualize rendered video. (Editor’s Note: The quality of this rendering had to be significantly lowered for the purposes of embedding a .gif in this blog)

I must say, we were pretty excited to see it come out!

We had plans to take a time lapse video through our cereal box pinhole camera…

But if you were in Henrietta during the eclipse, you got to see a whole lot of this:

Anyway, I hope you got to enjoy the eclipse yesterday (safely). I’m glad we got to see a rendering because we missed most of the real one! I also hope this article showed you some neat tools that can be used within SOLIDWORKS and Visualize for more than just work! If you have any questions on anything your read here, please do not hesitate to contact us! Thanks for reading, and as always, happy modeling!