Watching the Sun

Retirement is wonderful!

I'm often asked, "Are you keeping busy?"

• Reply # 1: I don't want to be busy. I want to be happy.
• Reply # 2: I'm busy being happy!
• Reply # 3: If busyness is measured by calories burned, I'm definitely busy!
• Reply # 4: Five long-term projects will keep me busy for the rest of my life.

One project is observing and imaging the Sun with my solar telescopes. For many years, both from home and from Winfree Observatory at Randolph College, I've observed the night sky . Obstacles, ever growing obstacles, make observing a dark sky increasingly difficult. I'm so very weary of obstacles!

• I'm often tired at night and less tolerant of sleep deprivation.
• It's almost always cloudy or partly cloudy in Virginia.
• The brightness of a nearly full Moon interferes with observing roughly half the nights that aren't cloudy.
• The often hazy sky is lit by light pollution from nearby street lights, shopping centers, and athletic fields.
• Trees block my view.
• A endless stream of cars travel up and down my street, headlights beaming, at all hours of the night.
• Worst of all are neighboring lights. Everyone, it seems, fears the dark. Unavoidable porch and window lights glare all night long. Giant, monstrous, unshielded mercury vapor driveway lamps blast their unnecessary light on the only place I can mount a telescope.   

Everyone loves light! Well OK! You want light? I'll give you light! The Sun! Is that enough light for you? 


The Sun is an extremely powerful light source, a four hundred million billion billion watt light! It's a naturally formed nuclear fusion reactor so powerful we feel its heat on our skin even 93 million miles away! (Think about that the next time you are sunbathing, and be grateful for Earth's protective atmosphere which blocks harmful solar x-rays and ultraviolet light.) The Sun is so bright we can hardly look at it without boiling our eyeballs!

So away with some of those pesky obstacles! I can observe the Sun during the day without loss of sleep. Surrounding lights are no problem in daylight, even the dreadful neighboring porch lights continuously burning around the clock! Full Moon? No problem! The Sun outshines them all! It even shines through haze!

"When applied to the Sun, the equations of physics bring off something quite miraculous: they make it transparent. The real Sun is transparent to neutrinos, whilst the simulated Sun is transparent to reason. We may read it like an open book. All the chapters concerning its inner workings, including its changes of color and other surface features, are spelt out in our enlightened computer printout."  - From: Stellar Alchemy by Michel Casse, Cambridge U. Press, 2003

Layers of the Sun (click for larger image)

Nuclear fusion occurs in the Sun's core shown in gray in the illustration above. Radiation from the core is degraded in energy as it works its way out to the Sun's surface where it is finally released to travel 93 million miles through space to warm our skin.

Obviously, I don't look at the Sun without a specially filtered telescope. My telescopes can reveal two outer layers of the Sun, the photosphere and the chromosphere. The photosphere is the ordinarily visible (yellow-white) solar surface. It can be viewed with my 8-inch Celestron Schmidt-Cassegrain telescope equipped with a mylar filter. The mylar filter blocks the overwhelming majority of intense solar light and lets through more light from the blue end of the spectrum than from the red end. Consequently, the Sun looks blue when viewed through the mylar filter. Here's an image taken from my driveway June 4, 2011 using a Nikon D40 DSLR mounted at prime focus on the mylar filtered Celestron-8. (Prime focus means the telescope itself serves as the camera lens.) Check out the sunspots.

One 1000th second exposure at prime focus shows sunspots (click for larger image)

The chromosphere is the region of the Sun just above the photosphere. If you've ever been privileged to see a total solar eclipse, you may have briefly seen part of the red chromosphere as a halo of "flames" around the rim of the black, totally eclipsed Sun. When the Sun is not eclipsed a special filter is needed to see the chromosphere. Just such a filter exists within my 100mm Lunt solar telescope. The filter is called a hydrogen-alpha filter because it allows passage of only one particular red color emitted by excited hydrogen atoms in the chromosphere. The Lunt telescope blocks all colors of solar light except for one very, very narrow red portion.

The Lunt 100mm solar telescope (click for larger image)

In the Lunt telescope the Sun appears in varying shades of red, dark red for less active areas, and almost white in active areas. Here is my first successful image taken on September 13, 2010. It shows a few flame like prominences on the Sun's rim and one small dark sunspot.

One 80th second exposure. Eyepiece projection. (click for larger image)

(Eyepiece projection means the camera, with its regular lens, is held close to the telescope's eyepiece.)


I first attached the camera at prime focus on the Lunt telescope on May 5, 2011 and was able to get this image of the entire solar disk. (A filament is a prominence seen against the Sun's disc instead of on the Sun's rim.)

One 60th second exposure at prime focus (click for larger image)

Notice how the surface details seem a bit fuzzy? Maybe the air was somewhat turbulent when the picture was taken. Or, perhaps, the focus wasn't precise. It's devilishly hard to determine precise focus through the camera's viewfinder!


Here's a sharper image image taken on June 8, 2011. It shows more surface detail, but not so many prominences.

One 100th second exposure at prime focus (click for larger image)

My experience so far tells me I need a different camera to achieve better images. The Nikon DSLR is made for taking color pictures of terrestrial scenes. Although it works very well for this purpose, it is not designed to take pictures of a monochromatic red light source like the Sun viewed through a hydrogen-alpha filter. When the Nikon images the red hydrogen-alpha Sun only one quarter of the pixels, the red sensitive ones, actually detect enough light to be useful. The remaining three quarters of pixels attempt to measure absent green and blue light, and are, therefore, practically useless. I soon hope to be imaging with a monochromatic video camera. Until then I'll continue to play with the Nikon.