April 2011 Meeting Notes
This month's business meeting included discussion of the upcoming St. John School Star Night, plans for Astronomy Day in May, interest in having a booth at Sunfest in June, and a request for a volunteer to coordinate on-line social media for the club. Following the business meeting, Joyce Gray-Ritchie summarized some of the more interesting recent astronomical news, and Duane Perkins showed a new sky darkness meter. Daryl Doughty presented the program, "DSLR Astrophotography".
What's News - Joyce Gray-Ritchie
After the business meeting, Joyce reported on several recent astronomical news items. Of particular interest were a couple of unusual supernovae discoveries. The first was a gamma ray burst that preceded an extraordinarily bright supernova, peeking at nearly one trillion! times brighter than the Sun. The extraordinarily intense release of energy in a very short period of time didn't fit the light curve of a typical supernova. Further investigation has suggested that the observation was actually of an entire star violently torn apart and completely swallowed by a supermassive black hole at the center of a galaxy over 4 billion light years (24,000,000,000,000,000,000,000 miles) away.
The second supernova article discussed a new theoretical study of "failed" supernovae. These enigmatic objects have been theorized for some time to occur when extremely massive stars undergo the core collapse that leads to the brilliant supernovae explosions seen in galaxies millions or even billions of light years away. But in a "failed" supernova, the star is so massive that its core collapse leads to the formation of a black hole so massive that all the photons created in the energy burst cannot escape, and are immediately swallowed up. From a distance, the star appears to simply collapse and completely disappear. For that reason it has been assumed that such events could never be detected, since no light escapes. But the new theoretical study suggests that it might be possible to detect neutrinos escaping from the collapse, holding the promise of some day detecting these extraordinary events.
Daryl Doughty reported that there will be a quadruple conjunction of Jupiter, Venus, Mars and Mercury in early May. The grouping will be at its most compact around May 10 and will appear low in the eastern sky about 45 minutes before sunrise. This should be a unique observing opportunity if you have an eastern view clear nearly to the horizon.
Duane Perkins showed a new sky darkness meter. Simply pointing it toward the sky and pressing a button results in an LED display of the overall "sky brightness" magnitude number, for the small region of sky it is pointing it. We look forward to using this at the St. John Star Night.
Speaker - Daryl Doughty
In this month's program, Daryl Doughty explained the basic characteristics and procedures of DSLR astrophotography. Beginning with a clear, yet detailed discussion of digital single lens reflex cameras, he explained the optics, sensor technology, pixel count, resolution and memory requirements of modern DSLR cameras. When selecting an appropriate camera for astrophotography, there are inevitable trade-offs between resolution, storage, weight and sensitivity. Additional important factors include spectral response of the sensor, programmability, computer interfacing and software support. For a variety of reasons, including extensive software for image downloading and processing, and extensive camera programmability and computer control, about 80% of DSLR astrophotography is done with Canon cameras.
With his own personal examples, Daryl demonstrated that DSLR cameras are very flexible for a wide variety of astrophotographic applications, including lunar, solar and planetary, wide field and deep sky objects. Many cameras now include live view capability, which is important for convenient, accurate focusing. Newer cameras also allow video capture, which can be important when capturing short exposure lunar or planetary images. This allows the astrophotographer to accumulate dozens or perhaps even hundreds of video images. With the appropriate software, these images can be aligned from frame to frame to eliminate jitter from wind or atmospheric disturbances, as well as compensate for drift from poor tracking. Once aligned, these images can be graded and limited, so that only the best images (those that occurred during brief moments of superior seeing) are stacked together to reduce the thermal noise that is always present, to some degree, in the sensor and electronics. Capturing dark frame images and flat field images during the astrophotography session provide additional information to process with the raw images, to further reduce noise.
Seeing the entire process from image capture through image processing was particularly helpful. Daryl used his DSLR camera to capture several images during the program, demonstrating the adjustments for shutter speed and ISO value. He also discussed several useful image processing programs, including Nebulosity, Deep Sky Stacker and Registax. Using the latest version of Registax, he stepped through the entire process of loading a video file of Jupiter images, aligning all the images in the file to eliminate movement, limiting the image sequence to the 50 best frames before stacking to produce a processed image. The final step was to apply wavelet processing, which significantly enhanced the image, and got an immediate positive reaction from the audience.
Daryl's presentation provided ample evidence that the advanced capabilities and considerable flexibility of modern DSLR cameras make them ideal for a broad range of astrophotography projects. More club members are now likely to consider this as the preferred direction for their own astrophotographic success.
Monday, May 2, Virgil Reese will present "Predicting the Future Evolution of the Universe"
in the Bartlesville Public Library Meeting Room. For more information, see the meeting announcement on our website home page at <http://sites.google.com/site/bartlesvilleastronomyclub/> .
BAS Public Website: http://sites.google.com/site/bartlesvilleastronomyclub/
BAS Yahoo Group: http://tech.groups.yahoo.com/group/BvilleAstro/
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