Make a telescope

What can we use instead of the larger and shorter focal length lenses or black construction paper if those are hard to find?

Substitute two magnifying glasses of different strengths for the larger focal-length objective and the shorter focal-length eyepiece, and use black paint or black electrical tape in place of black construction paper while still lining the insides and taping the lenses as instructed.

The image stays blurry even after sliding the small tube—what might be wrong and how can we fix it?

Check that both lenses are centered and taped flat to the tube ends, the insides are dark from the black construction paper to prevent stray light, and the small tube can slide freely with about a two centimeter overlap—if it sticks or rubs, sand or trim the cut edges so it moves smoothly, then re-mark the sharp focus with the marker and masking tape.

How can we adapt this telescope activity for a 4–6 year old versus a 10–12 year old?

For 4–6 year olds have an adult measure and cut the large tube to ~30 cm and the small tube to ~25 cm and pre-attach lenses while the child helps line the tubes and slides to focus, whereas 10–12 year olds can do the measuring and cutting with supervision, experiment with different lens combinations, and record their Moon observations to share on DIY.org.

How can we improve or personalize our telescope after building it?

Personalize and enhance it by painting the exterior, adding a smartphone holder over the eyepiece to photograph the Moon, mounting it on a simple tripod for steadier viewing, and labeling the focus mark with decorative tape before sharing a photo or description on DIY.org.