Summer Sun


Now that Summer is upon us, I’ve been using a hydrogen-alpha solar telescope to take pictures of our Sun:

Sun

Taking pictures of the Sun is quite different from the “deep space” photography that I normally do.  It actually felt weird to be taking pictures in the observatory during the day.  And the exposures are so short!  With deep space images you need to capture multiple long exposures and “stack” (combine) them to reveal the dim details.  You can’t do very much stacking with solar images because the details actually change pretty quickly, so they would become blurred in a combined image.  Also, when photographing the Sun you are looking right at the very thing that creates the atmospheric turbulence that plagues all astro-photography (the Sun is about half a degree wide, so it requires fairly high magnification).  So instead of combining a handful of long exposures, you shoot many short exposures, then select the best ones (the so-called “lucky” frames where the turbulence is not so bad), and throw away the rest.  This is the best of 124 frames, selected by visual inspection.

I still have a lot to learn about capturing and processing solar images, but am pretty happy with this is a first attempt.  Here’s a blow-up of the lower right corner, showing a bit more detail:

Sun

Here you can see some of the structure around the sunspot, and more of the smaller prominences around the edge.

As noted above, this is a hydrogen-alpha image, which is one of the bands I use in photographing emission nebulae.  But in this case the filter is much narrower, 0.7 Angstrom, which is 0.07 nanometers.  The filters I use for emission nebulae are 3 nm, or about 43 times as wide.  That is what makes solar telescopes so expensive.  The good news is that because the Sun is so bright, you don’t need a very large telescope to see it.  The one I used is just 60mm aperture.  Please note:  It is extremely dangerous to look at the Sun through a telescope or binoculars unless it has suitable filters.  The intensity of sunlight through even a small telescope is enough to permanently blind you before you can even blink.

Perhaps the most important thing about solar photography is doing it at the right time.  Unlike deep space, the surface of the Sun changes quickly.  Over the hour or so that I spent capturing 124 frames the larger features were fairly constant, but if you look at it more closely you will see that smaller details are different in frames taken just minutes apart.  And sometimes these features become very dramatic, such as when there is a coronal mass ejection (CME).  That is what solar astronomers live for!

 


About Greg Marshall

I am a retired electronics engineer and after a few months of enjoying my leisure I began to miss doing product development. My astronomy hobby always needed new solutions to unique problems, so I decided that whenever I came up with a good solution I would try to make it available to others.

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