Sun of a Gun!

See sun spots, the transit of venus...featured on TV!

The stars only come out at night, right? WRONG!

Build a DIY telescope that lets us look at stars in the daytime and study the closest star to Earth safely during your lunch break!

Why can't I see the stars during the day time?

As a matter of fact, the stars do come out in the day, they are shining in the sky all the time. It's just that the Sun is so bright we can't see the faint starlight compared to the brilliance of the Sun's light. Imagine having a torch with very flat batteries. The torch doesn't seem to light up at all when you try it out in the sunshine. Try it in a dark room at night and still glows faintly, we just couldn't notice it during the day.

So the stars are there in the day, but what about the problem of the Sun? You might think that it is so bright that we'll never see stars in the day...but you would be forgetting one thing...

The Sun is a star, the closest star to our planet. That is why it is so bright. The other stars we see at night are also suns, some the same size or bigger than ours. The reason they appear small and dim is because they are so very far away from us. It's a bit like looking at car headlights when they are close to you, they look large and bright. When a car is far off in the distance, the light looks smaller and less bright even though the size of the headlamps haven't really changed! If our sun (a star called Sol) has planets going around it, perhaps the other stars do to....

By building a special attachment for a telescope, we can safely look at the Sun, learn about stars, and still get home in time for tea...

The need for a safe sun viewer...the Sun Gun

Because the light from the Sun is so bright and intense we NEVER LOOK AT THE SUN DIRECTLY THROUGH A TELESCOPE OR BINOCULARS. You will be blinded, perhaps permanently.

Many of us have probably projected an image of the sun onto a piece of card for safe viewing instead. The Sun Gun idea was a modification of this and an article appeared in Scientific American in 2000. As a Physics project, the Inglewood High students had to learn about light, lenses, real and virtual images and levers while trying to apply their knowledge.


Here an inexpensive spotting scope is fitted with an adapter at the 2003 Science Fair.

  1. A piece of pipe that has a suitable diameter so that it will slide over the eyepiece is pushed through a hole cut into the bottom of an old plastic paint container.
  2. The pipe is fixed to the base of the container via a screw-threaded flange. The interior is painted matt black with spray paint and left to dry.
  3. The lid of the container has its entire centre cut out leaving only the rim providing a 1cm flat lip once it is pushed back onto the main body of the container.
  4. A sheet of "RediDraw" Draughtsmans tracing film (polyester) makes an excellent and inexpensive projector screen.
  5. Cut to an appropriate size it can be temporarily fastened to the flat 1cm lip using adhesive gum, velcro, etc, so it can be removed for safe storage or easily replaced if damaged.
  6. Filters attached to the front of the telescope result in much sharper images and more detail can be seen than our initial attempts and digital photography show below (can you see the Sun spots on the left?).

A better quality telescope also provides better images though the scope we used was quite satisfactory for the simple observations and demonstrations that most teachers will undertake. A piece of card cut as a large square about 50cm across placed over the front of the telescope (cut a hole in the centre of the card the diameter of the telescope tube) provides some shade that gives the eye better contrast when looking at the image projected at the back.

The tripod set up was OK but was prone to wind wobble and any bumps of the leg as students crowded around. A permanent mount could be erected in a convenient location in a school. This would provide more stable arrangement than our simple tripod would permit. Regular observations of the Sun and Sunspots could be undertaken by students and perhaps the period of rotation could be determined.

The sun will move across the projector in proportion to the magnification used. I used a mid-range magnification so I only had to swing the telescope around to follow the sun every few minutes.

A sturdy post to attach the telescope to is required and a sun tracking motorised mount could be made (eg, use to LDR’s and measure resistance between them; the motor moves until both show the same resistance). You just have to point the telescope in the right direction once, then take photos or record video more easily.

It is also possible to use this as a solar observatory during the transit of Venus.

In New Plymouth "The Art Shop" stocks the polyester film we used but you might like to try other materials such as thermal drape lining. I do not recommend paper since the fibres are easily visible in bright light!

Ask the experts for more information while visiting the New Plymouth observatory. The members of the Astronomical Society hold open nights every Tuesday night between

  • 8pm till 10pm in the Summer

  • 7:30pm till 9pm in the Winter


  1. Make a model planet that floats in the air! A fascinating Solar System to build...
  2. Lunar Lander - use nothing but air to steer a spaceship to safety
  3. Discover the hidden information about the planets in our Interactive page
  4. Move the planets around on screen! organise the planets in the correct order in our Interactive page
  5. Try to find out what stars are made of and how they are different from each other.
  6. How do telescopes work?
  7. What is the difference between stars, planets, meteors, asteroids and comets?
  8. What is a Black Hole?
  9. When is the next transit of Venus? How is this connected to Captain Cooks voyages?

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