If you want a stable oscillator, you usually think of using a crystal. The piezoelectric qualities of quartz means that it can be cut in a particular way that it will oscillate at a very precise frequency. If you present a constant load and keep the temperature stable, a crystal oscillator will maintain its frequency better than most other options.
There are downsides to crystals, though. As you might expect, because crystals are so stable it’s hard to change the frequency much when you want a different one. You can use a trimming capacitor to pull the frequency a little, but to really change frequency, you have to change crystals.
There are other kinds of oscillators that are more frequency agile. However, they aren’t usually as stable. To combine flexibility with crystal-like stability, you can use a Phase Locked Loop (PLL). Many modern systems use direct digital synthesis, but the PLL is a venerable and time-tested technique.
The SEM sprang to life and gave [Macona] and a friend their first images. However, SEMs are finicky beasts. Eventually the filament burned out and needed to be replaced. New filaments are $500 US for a box of 10, which is more than [Macona] wanted to spend. It turns out filaments can be built at home. A bit of .089mm tungsten wire and a spot welder were all it took to fix the issue. Next to go bad was the scan amplifier. While SEMs use many exotic parts, the Hitachi used relatively common Sanyo STK070 audio amplifiers for the purpose – an easy fix!
[Windell and Lenore] from Evil Mad Scientist Laboratories brought a few hacks along. They picked up an old Radio Shack music player chip at the 
[Cal Howard] brought his DIY VR goggles. [Cal] converted a Kindle Fire into an Oculus Rift style head mounted display by adding a couple of magnifying lenses, some bamboo kebab sticks to hold the lenses in place. Judicious use of cardboard and duct tape completed the project. His current hurdle is getting past the Fire’s lack of an accelerometer. [Cal] planned to spend Sunday at Maker Faire
