Relive the Discoveries of Galileo September 2014 | Page 15

The Durham Region Astronomical Association How to relive Galileo’s discovery There are three safe ways to observe the sun: 1 Project its image through a pinhole and onto paper 2 Attach to the front of a telescope a genuine solar filter designed specifically for viewing the sun 3 View the sun through a solar telescope designed for viewing the sun safely, such as solar telescopes from Coronado or Lunt. Looking at the sun any other way is dangerous and could cause permanent blindness. 1. The pinhole method is easy, but the resulting image may be too small to display sunspots. However, it is a fun exercise, demonstrating how a small hole can produce a sharp image. Take a large cardboard box with one open end. Cut a small square in the centre of the side opposite the opening. Tape tin foil securely on all sides over t he sq uar e. Carefully put a tiny hole in the centre of the foil with a pin. Set up the box with the foil end facing the sun. Hold a sheet of paper behind the hole in the box’s shadow. You’ll discover the farther you hold the paper from the hole, the bigger but dimmer the sun’s image will appear. Note: Some low-cost telescopes in the past were supplied with cheap solar filters that were designed to be attached to the eyepiece. If you ever see one of these filters, do not use it. Better yet, throw it out! 2. The best way to see the sun well enough to draw is through a telescope equipped with an astronomical solar filter attached at the front. You can make your own solar filter by purchasing aluminium-coated solar filter material. You can also purchase pre-made solar filters to fit your telescope. Visit an astronomy store or its web site to inquire about obtaining solar filter material or a ready-to-use filter. To learn more, read this Sky and Telescope article online: http://www.skyandtelescope.com/ observing/objects/sun/3304056.html. 3. Two telescope companies offer Solar Telescopes: Coronado (http:// www.coronadofilters.com/) and Lunt Solar Systems (http://www.luntsolarsystems.com/). The entry-level scopes they offer (around $500) are very popular, providing a safe way to see not only spots, but solar flares and prominences! It expands astronomy to the daytime, making it safe and fun to observe our nearest star and watch its dynamics. Bear in mind that the sun goes through an 11-year cycle of varying activity. As 2010 opens, the sun is nearing the end of solar minimum during which there are few, if any, sunspots. In the coming years, as the sun approaches solar maximum, spots will become more plentiful. So, if you make or buy a solar filter or solar telescope, don’t be surprised if the sun first appears as a featureless disk. Keep checking and in due time, you will see plenty of spots that you can draw in the circles provided below. - 15 -