Author Topic: Sun photography = DANGER!  (Read 3340 times)

hip17702

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Sun photography = DANGER!
« on: June 27, 2013, 07:33:37 PM »
Having asked the community for some help about a specific aspect of sun photography I would like to stress with you the danger inherent to this activity:

Never look or picture the sun directly, especially with teleobjective, without specific filtering. Any mistake can have devastating consequences on your camera, your eye, or both!

Light coming from the sun not only contains visual wavelenghts, but also a huge amount of UV and IR light. So even if the image seems not dazzling, IR and/or UV can still be harmful! The "trick" consisting to blacken a sheet of glass with a candle to make a homemade filter is not safe at all. Using a very dark grey filter, or stack of them is not safe at all. Any solution not specifically designed to observe the sun will be dangerous!

If you need to picture the sun please to not hesitate to ask a specialist around you (mainly astronomy club) about specific filtering, or drop me a message I will be happy to help.

albert-e

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Re: Sun photography = DANGER!
« Reply #1 on: June 27, 2013, 09:45:27 PM »
You can maybe give us any suggestions on how to protect the users.

hip17702

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Re: Sun photography = DANGER!
« Reply #2 on: June 27, 2013, 11:32:24 PM »
With pleasure  ;)

In order to observe or photography the sun in total safety the best is to use a safety filter that covers all of the light entry, specifically designed for solar observing.

Several decades ago it was done with a special -thus expensive- coated optical glass who has to be perfectly plane and with perfect parallel faces, otherwise the optical quality was compromised. Today mylar films with the same coating exists for a few bucks. The thin mylar film has to be placed front of the objective, and do not need to be flat due to the fact the several ┬Ám of the film's thickness has no incidence on the optical quality. Cheaper and easier to use, yet more fragile.

When you have some mylar film mounting it on an objective is up to you: fix it with some tape or rubber band (not recommanded because it may fall off while observing) like this: http://www2.ville.montreal.qc.ca/planetarium/Information/Dossiers/EclipsePartielle2011/filtre_mylar.jpg, or better build a filter support with some cardboard you can paint in black (to avoid light reflections), or even buy a complete set with mylar film and aluminium frame ready to be placed front of your objective with three nylon screws.

Another clever way to use the film (that comes mainly in rectangular sheets) is to build a rectangular frame to place front of any objective, like this: http://photographingtransitofvenus.files.wordpress.com/2012/05/20120527-img_6033.jpg?w=650&h=488

Before putting your eye at the camera or starting liveview place your hand behind the finder. If you see a bright spot of light point away from the sun and carefully check your setup.

To find mylar film sheet and related accessories please google "solar filter film". You will find anything you need, from advices to create a safe filter to ready-to-use commercial solutions.

If you have further questions please do not hesitate.

albert-e

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Re: Sun photography = DANGER!
« Reply #3 on: June 28, 2013, 02:11:53 AM »
That was good advice. Thanks.