The Story of an Astrophoto

Rodger Fry hoped it would be a world-class image.

The photo of the Crab Nebula was taken the night of Jan. 15 by the Faulkes two-meter (78-inch) diameter telescope on top of the Haleakela volcano in Maui, Hawaii. But the 27 amateur astronomers who took it were thousands of miles away, ensconced in Bob Moore’s office in Salt Lake City, controlling the ‘scope through an Internet link.

[Faulkes Telescope North view of the Crab Nebula taken by members of the Salt Lake Astronomical Society the night of Jan. 15 and assembled by Tyler Allred. A full-sized view can be seen on Allred’s SLAS album by clicking HERE and then clicking the image again.]

Briefly, some background. As noted by Nightly News on Dec. 27 — click HERE — the Faulkes Telescope North is part of the Las Cumbres Observatory Global Telescope Network, a British private foundation hosting telescopes around the world for scientific research and research-based education. Founded by British philanthropist Dill Faulkes, the observatories are dedicated to bringing high-quality astronomy to British school children. Because the Faulkes telescope is on Maui, 10 percent of its use is earmarked to research and outreach by the University of Hawaii. The Salt Lake Astronomical Society is involved because of its own extensive outreach and education programs and its deep interest in the Maui project.

[The Faulkes Telescope North on Maui, photo by Rodger Fry]

In May 2009, a jolly gang of SLAS members, wearing yellow Hawaiian shirts bearing the society’s beehive-observatory emblem, toured the Faulkes Telescope North. During their “Tropic Telescopic Tour” they met a couple of former Utahns who work with the Haleakela telescopes, J.D. Armstrong and SLAS member Rob Ratkowski. They enjoyed an incredible view from the volcano but an Internet glitch prevented them from operating the Faulkes.

[Tropic Telescopic Tour members visit the Faulkes Telescope North. Photo courtesy of Rodger Fry]

The society’s first experiments with the Faulkes instrument in December, operated in Moore’s office with Armstrong’s guidance, produced some interesting views. But they don’t compare with the stunning image of the Crab Nebula taken on Jan. 15.

That evening, Utah astronomy lovers crowded into Moore’s conference room, delighted that the telescope was theirs to borrow for an hour and a half. Conditions in Hawaii were beautiful. Moore called Ratkowski on Maui and asked what the astronomical seeing was like, and “he said that he felt it was so good you would only expect one night every five years to be that perfect,” noted club Vice President Rodger Fry, who coordinates the Faulkes efforts.

“We came armed with a list of 26 targets but had to choose which targets and how many could be imaged,” he told Nightly News. “We had the option of taking moderate quality images of up to three targets or spending all our time on image and producing a ‘world-class’ image.”

A multiplicity of views of one target is better than a few views of several targets because astronomical images can be “stacked,” or combined, to reduce the noise that creeps into any photo. A slight blurriness in one section of a photo, caused by air turbulence, is overwhelmed by the other photos where that site isn’t blurred. To an extent, the more photos that don’t show that particular flaw are stacked, the less noticeable the flaw becomes.

“Fortunately, the advice of the most experienced astrophotographer in our group was taken and we spent about 80 of the 90 minutes we had access to the telescope on one well-selected image, the Crab Nebula.” Fry noted that in Hawaii the Crab, also known as M-1, was high in the sky, meaning there was less atmospheric flow for its light to cross. It was “just the right size for the telescope’s field of view and is an exquisite target.”

For a history of the Crab and my own first attempt to photograph the nebula with my 12-inch telescope, see my Oct. 23, 2009, blog, posted HERE.

“This opportunity was something special,” the club’s Tyler Allred said by email. “It was really fun for me to get a chance to work with data from such a large scope. When we started the session, I felt like we were groping in the dark, but we quickly got our act together and captured some nice looking photons. I can’t wait for our next imaging session!”

Larry Holmes, an SLAS member who also was present, commented that astronomy reminds him of what the archaeologist Howard Carter said when King Tut’s tomb was opened. Carter peered through a hole he had made in the final door of the boy king’s tomb and saw, by the light of a candle, animal statutes, figures of snakes, and gold. His sponsor, Lord Carnarvon, asked him if he could see anything. Carter managed to get out, “Yes, wonderful things.”

Astronomy makes him paraphrase Howard Carter, Holmes said, “except I would say, ‘We see many wonderous things.’ Or, from the wonderful movie, ‘Come, see the work of the Lord.'”

According to Fry, the group was able to take 16 different exposures, some without filters and others with red, blue, green, Hydrogen-alpha, beta, and oxygen III filtration.

“You could feel the excitement in the room generated from the enthusiasm of the 27 attendees,” he added. “Each time a preliminary image appeared on the monitor, you could hear oohs and ahs.

“After our session, we drove to an all-night diner and celebrated our victory.”

Allred, a master astrophotographer, took on the task of preparing the combined image, using computer programs. First he got all the views into register by aligning the stars. Then he created a black and white image using data from pictures taken with no filter and blue, green, red, oxygen III and Hydrogen-alpha filters.

Then he created separate color data images using red, green and blue and Hydrogen-alpha filters. (The later was added to the red values, at 60 percent red and 40 percent H-α.) The three were combined to create a color image. “The black-and-white layer … was then added to the color image as a luminous layer.”

The result is what astronomers call an LRGB image, for luminous-red-green-blue. Minor imperfections, such as pixels that showed up pure white or jet black, were removed using the PhotoShop program, he said

Allred’s web site explains some of the Crab’s wonders that are visible in the view:

“The image nicely illustrates the intricate structure of this remnant of a huge supernova. … The nebula has a spinning neutron star at its core that has been dubbed the ‘Crab Pulsar.’ This neutron star has a spin rate of roughly 30.2 revolutions per second, and it is extremely energetic: giving off radiation at wavelengths from gamma rays to radio waves.

“The pulsar has been creating shock waves that can be seen near the center of this image as concentric arcs. These shock waves have been captured in many images and their speed has been computed at an astounding 24,000 km per second [nearly 15,000 miles per second], or nearly 8 percent of the speed of light. The diffuse blue light, called synchrotron radiation, is emitted from curving electrons traveling at up to 1/2 the speed of light.”

Thanks to the generosity of benefactors in Hawaii and Great Britain and their own talent and perseverance, Utah amateurs have taken a world-class astrophoto.

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