How To Choose Safe Solar Equipment

As the total solar eclipse of 2017 draws near, it is important to know which equipment you will need to observe the sun safely.  We also have some tips on observing or taking pictures of the Sun that are safe for the whole family and will help you capture perhaps the biggest solar event of the century.

Solar Observing Myths

Let's get some myths about viewing the Sun out of the way first:

  1.  Welding glass is not solar safe.   While very dark, welding glass - the kind found in welding glasses or hoods - does not block UV to the extent you need and will not prevent the interior of your telescope or camera from getting extremely hot.
  2. Neither are sunglasses.  No pair of 'regular' sunglasses on the planet offers the kind of UV protection your eyes need for viewing the Sun.
  3. Standard Mylar is not acceptably safe for extended viewing of the Sun and should not be used to make solar filters.

What makes a filter safe for solar observing? The filter needs to allow a very specific wavelength of light to pass through while blocking out harmful UV and excessive heat.  There are several materials that are acceptable for solar observing and imaging each with different branding or features but they can be broken down into two basic categories:

  • White light solar filters and film
  • Narrowband solar filters and telescopes

White Light Solar Filters and Film

White light solar films are the most economical choice and highlight the surface details of the Sun producing a greyish-white image.  This is, in reality, closer to the white light produced by the Sun.  These specialized films are available in sheets to custom make filters, stretched on a filter frame and applied to glass substrates.  You'll be able to see Sun spots and surface detail depending on the quality of the filter and the power of your telescope.   White light solar filters are made to fit traditional DSLR lenses up to large aperture Schmidt-Cassegrain and Newtonian telescopes. Most film and solar safe white light materials are developed for observing and can be used for photography, though there are specialty photography films available meant strictly for imaging the Sun.

Narrowband Solar Filters and Telescopes

Narrowband filters permit a very small portion of the light spectrum to pass through.  Most commonly you'll find H-Alpha solar filters and telescopes.   H-Alpha dedicated telescopes are a sealed, complete unit and consist of a primary filter a tuner of some kind and a secondary blocking filter.  These telescopes are a great choice if you are doing outreach where people with little to no experience will be using your equipment.  They are the safest option being difficult or impossible to remove the filter. H-Alpha also produces a yellow-orange false color image of the Sun which we perceive as the "natural" color of the Sun thanks to our atmosphere.   H-Alpha filters will show you an incredible amount of detail, that increases with the aperture of the telescope just as with night sky objects.  Solar flares, in particular, are prominent and the fascinating swirling surface of the Sun is visible.

A popular alternative to H-Alpha is Calcium K filters and telescopes.  Calcium solar filters produce a blue-violet image of the Sun.  Typically used for imaging, these filters pass a different wavelength of light than H-Alpha that can read as a higher contrast image.  As we age, the lenses of our eyes yellow meaning a yellow/orange image would make it more difficult to see finer details as contrast lessens.   If you do have low contrast vision, Calcium filters make an excellent choice.

Narrowband solar equipment is more fine tuned and requires higher precision in manufacturing, so you will find that these solar instruments are higher in price than a standard white light filter.  However dedicated solar telescopes can be had for well under $1000 and will provide a high detail view of the Sun.

What Type of Gear to Choose

Determine your budget.  White light solar filters and film range from $30 and up.  H-Alpha solar telescopes start at about $700 although you will find them available on sale for less from time to time.

If you already have a quality telescope and your budget is tighter, white light or black polymer are the way to go.  If your budget allows, piggybacking an H-Alpha telescope on a standard telescope outfitted with a white light filter will allow you to have side by side views of the Sun.  One could be used for imaging or video while the other is dedicated to live observing.

If you have a crowd to provide gear for or children, inexpensive solar safe observing glasses are available. These glasses are fitted with a type of solar material, typically black polymer, and are an easy way to observe the Sun and enjoy a total solar eclipse.  While safe for children of all ages, children under the age of 12 should be closely supervised as removing the glasses could be at the least painful and at worst could be damaging the eye.

Learn more about the exciting world of solar astronomy, be prepared for the 2017 solar eclipse and if you need any help in choosing your gear the staff at Woodland Hills Camera & Telescopes are here to help.  Call us at 818.347.2270, chat with us or email us.


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