Tuesday, June 5, 2012

Viewing the Venus Transit

Viewing the Venus Transit requires special preparations. The transit is on the face of the sun, so direct viewing is impossible. Remember that direct viewing of the sun with the eyes is dangerous and doing it with an optical aid such as binoculars or a telescope may cause permanent damage and blindness. Do not use improvisations such as old floppy disks, old films etc.
The instructions are also suitable for a Solar eclipse observations. 

After this warning here are some options to view the Venus transit.
Solar Eclipse Glasses
  1. Get special solar eclipse glasses. These are special glasses, with special filters which block almost 99.99% of the sun light. Such glasses are not expensive, and will be very useful for future solar eclipses (there will be a full solar eclipse in 2017 in the USA). However, such glasses are to be used with the eyes only, and not through a telescope or binoculars!
  2. If you have a telescope you might want to consider to purchase a Solar Telescope Filter for it. There are generic filters which are suitable for many telescopes and there are vendor specifics filters for the vendor brands. You can buy at Amazon or at your local dealer. These filters are attached to the telescope, in front of it and block the light BEFORE it enters the telescope. Such filters MUST NOT be used instead of an eyepiece. The light from the sun must be blocked before it is concentrated by the telescope (the filter is not strong enough to block the light after the telescope concentrates it). During the observations make sure that the filter is strongly attached and that no one removes it by mistake (especially when you are doing an observation with a group of people).
  3. If you are really into solar viewing, you should consider purchasing a dedicated solar telescope. Such telescopes as the Coronado PST are dedicated and safe for solar viewing and are useful to observe other interesting solar phenomena such as the sun prominence.
  4. If you have a telescope and you want to project the image to a large audience you can use the projection method. Basically you project the image of the Sun to a dark surface (make it in the shade) and focus. Sunspots are very visible this way. This method is appropriate for small refractors and Newtonian telescopes, but not for SCT telescopes. If you are not sure how to do it or if it is suitable for your telescope do not do it! Personally, I do not like this method very much since I think that if you already have a telescope, it is a very little investment to buy the filter. Take note that the intensity of the sun light may harm the telescope as it creates heat which can harm the plastic and the optics so do it at your own risk. Also make sure that no-one ever tries to look through the telescope at the sun. Full instructions are here
  5. You actually don't have to own a telescope to project the sun. You can build a great homemade pinhole projector from simple boxes. You will get a small image of the sun and you will be able to see a dark spot on it.
  6. If you do not have the solar glasses nor a telescope, join your local astronomy club. The transit is a major event and professional observatory and local amateur groups will provide the means for the public to view the transit. 
  7. Join a live web cast of the event. Many observatories from around the globe will host live cover of the event. You will be able to view it safely from your home. However, I think that this is the less preferred option to view the transit (just one step away from not viewing it at all) as there is no replacement for viewing with your own eye.

Projecting the sun through a telescope


  1. Have you tried looking at the sun through two layers of 3.5" floppy discs? It's quite a good filter, actually.

    1. Do not use old floppy discs, they do not block enough of the sun rays and they do not block all wavelengths.

  2. What about two layers of 5 1/4" floppy discs attached to polarized uv protected sunglasses?

  3. Do you have any updates about when will be the next astronomical phenomenon, like the next eclipse? The last annular eclipse was great (the one with the ring of fire around the moon), there were sessions that taught spectators how the eclipse should be properly viewed.

  4. Nice! I'll prepare for myself. Thanks for recommending me now.