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Projection with a small telescope

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A small telescope provides a larger solar image than can be obtained with binoculars, and a much shorter projection distance.
Photo: Espace pour la vie

Projection with a small telescope (refractor or reflector)

A small telescope provides a larger solar image than can be obtained with binoculars, and a much shorter projection distance. Place an eyepiece in the instrument: Chose a low power ocular. In the case of a refractor, you have the option of inserting a star-diagonal between the focuser and the eyepiece itself: This arrangement will project the image at right angles to the telescope. Don’t forget to cover your finder scope, or better yet, remove it completely.

Centre the Sun by moving the telescope until its shadow appears the smallest. Project the Sun’s image onto a white cardboard placed about 20 cm from the ocular. Focus the image using the telescope’s focussing knob. You can reduce ambient light reaching the screen by placing it inside a box: The Sun’s image will have improved contrast. Some commercial telescopes come equipped with a projection screen and mounting bracket. These are practical but not essential.

Important note: The telescope’s opening should not exceed 5 cm (2") to avoid overheating and damaging the eyepiece. If necessary, construct a diaphragm by covering the opening with cardboard that has a 4 to 5 cm hole cut into it. The dust caps of some instruments are already fitted with a small hole covered by a cap. These are ideal. Make sure the dust cap, or cardboard diaphragm, is securely taped in place to avoid accidental removal.

Warning!
Never leave this apparatus unattended: No one must ever look through the eyepiece while the instrument is pointed at the Sun.

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