Solar Projector / Sun Funnel

This is a 3D printed version of the Sun Funnel that NASA published the instructions for building. You can find that here: https://eclipse2017.nasa.gov/make-sun-funnel

I wanted to customize the sun funnel to allow a larger projected image and use a larger eyepiece that I had on hand. The size of the projected image will depend on your telescope's focal length and the focal length of the eyepiece that you use. The document from NASA linked to above shows the math.

I'd recommend picking an eyepiece that makes a solar image that is 3-4" in diameter for this 6" diameter screen. That way there is some wiggle room allowing you to not have to continually track the sun but let it drift across the screen then reposition. Of course if you are using a tracking mount, then choose an eyepiece that fills the screen more 5-5.5" perhaps.

While it's possible to use super cheap eyepieces like Plossl's will work, having a bit wider FOV makes it easy to find and keep the sun in view longer for th