The projection method
Caution!
Never look into the telescope, if it is aligned to the sun. cornea lens and retina will scorch immediately. Your eye is destroyed irreparably by the extremely bundled solar power.
However the telescope can be used as projector, since the sun exhibits a very high light intensity. Easily I caught a 10 cm a large picture of the sun on a screen, while the eyepiece was attached in approximately a distance of 20 cm.

Advantages of the projection method:
We receive large pictures of the sun. With my telescope (objective diameter 4 ", focal length 1000 mm, eyepiece focal length 9.5 mm) sun pictures are up to a diameter of 38 cm possible.
  • Several observers can look at the sun picture on a screen at the same time.
  • The pictures can be drawn at the screen, if this is fastened stable.
  • The method is economical.
Fig. 9: Projection method

Disadvantages of the projection method:

  • Accurate aligning of the screen is necessary for distortion-free pictures.
  • The screen must be adjusted at the telescope to avoid the sun run.
  • The aligning of the telescope to the sun is difficult, since you cannot in-look directly into the eyepiece (see above).
  • If refractors heat up locally by absorption cemented lenses may misalign. Using reflectors the mirrors may distort.
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