Bahtinov Masks

The thing that has probably blown my mind the most about all of this equipment is the Bahtinov mask. Invented by an amateur astronomer, it completely trivializes focusing.

You just place this over the aperture of your telescope, point it at a bright star, and adjust focus until the three diffraction lines are centered. It is absolute magic! The following image shows proper focus with the mask on a star.

And the following GIF shows how the image changes through focus.