Astronomical Telescope

How to build an astronomical telescope!

1. 2 lenses (1 objective, 1 ocular)

2. 1 meter stick

3. 2 lens clamps

4. One flashcard

5. One flashcard holder

6. One tube

7. Hot glue

1. Take the ocular lens and put it inside one of the lens clamps, then attach the clamp to the meter stick

2. Attach the note card to the other kind of clamp and attach that to the meter stick as well.

3. Make sure you are in a room with natural light (a window). Slide the note card back and forth until the image from the lens is as clear as possible. Measure the distance between the lens and the note card. Record that number as the focal length of the ocular lens

4. Repeat steps 1-3 with the objective lens to measure its focal length

5. Attach both lenses to the meter stick using the lens clamps

6. Add the two focal lengths together. The distance between the two lenses should be the sum of the focal lengths

8. Take the 50 cm tube (has to be longer than the sum of focal lengths) and cut a slit down the middle of one side of the tube. Put ocular lens at the end of the tube, fixing it with hot glue but leave the objective lens unfixed, to be able to adjust the focus as needed. (start at the sum of focal lengths)

Put your eye up to the ocular lens and aim the end of the telescope at what you want to look at. Slightly move the objective lens along the tube to perfectly focus the image.

The image is upside down because the shape of the lenses cause the rays cross, therefore flipping the image

The equation is:

M= Fobjective / Focular

Example: Focal length of objective: 17cm

Focal length of ocular: 5cm

M=17/5

M=3.4