Build an astronomy flashlight

What can we use if we don't have a 220 ohm resistor, slide switch, or aluminum foil?

You can substitute a higher-value resistor such as 330Ω or 470Ω (it will make the LED dimmer), replace the slide switch with a small switch salvaged from an old toy or make a simple touch switch by separating and touching the taped wires, and line the tube with white paper, shiny gift wrap, or mirror craft paper instead of aluminum foil to reflect the red light.

My LED doesn't light—what should I check first?

Check that the two AA batteries are placed matching the + and - marks in the battery holder, the LED's longer leg is the one with the resistor attached and taped to the switch terminal per Steps 2–5, the LED's shorter leg is taped to the battery negative wire, all exposed metal is covered with tape to avoid shorts, and the slide switch (Step 12) is flipped on while feeling for any loose connections.

How can I adapt this activity for younger or older kids?

For preschoolers have an adult do the twisting/taping of the resistor and LED and let the child do foil lining and decorating the cardboard tube, while older kids can solder connections, add multiple LEDs, build a star-pattern stencil to project constellations, or experiment with different resistor values to see brightness changes.

How can we extend or personalize the finished astronomy flashlight?

Personalize it by painting or covering the cardboard tube, cutting a star-shaped stencil at the tube end to project constellations, swapping the slide switch for a small potentiometer to dim the LED, or adding mirrored craft paper and extra LEDs inside the tube for a stronger, customizable beam.