I was wondering exactly what the GONG images were and I stumbled on this abstract, as well as a presentation on the instrument. It uses a Daystar Quantum PE 0.4 angstrom. They apparently also evaluated Coronado and Solar Spectrum.
"Since mid-2010 the Global Oscillation Network Group (GONG) has collected H-alpha images at six sites around the world. These images provide a near real-time solar activity patrol for use in space weather applications and also an archive for research purposes. Images are collected once per minute, dark, smear, and flat corrected, compressed and then sent via the Internet to a 'cloud' server where reduction is completed. Various reduced images are usually available within a minute after exposure. The H-alpha system is an add-on to the normal GONG helioseismology instrument and does not interfere with regular observations. A polarizing beamsplitter sends otherwise unused 656 nm light through two lenses to a Daystar 0.04 nm mica etalon filter. The filter is matched to an image of the GONG light feed entrance pupil and sees an image of the Sun at infinity. Two lenses behind the filter form the solar image on a DVC-4000 2k x 2k interline transfer CCD camera. Exposure times are automatically adjusted to maintain the quiet disk center at 20% of full dynamic range to avoid saturation by bright flares. Image resolution is limited by diffraction, seeing and some high-order wavefront errors in the filters. A unique dual-heater system was developed by Daystar to homogenize the passband characteristics of the mica etalons. The data are in regular use for space weather forecasting by the U.S. Air Force Weather Agency, which funded construction and installation of the instruments. Operational and reduction improvements are underway and archived data are already being used for research projects. The Web site URL is http://halpha.nso.edu."
American Astronomical Society, SPD meeting #42, id.17.45; Bulletin of the American Astronomical Society, Vol. 43, 2011, May 2011
Full-disk Solar H-alpha Images From GONG
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Re: Full-disk Solar H-alpha Images From GONG
Interesting, thanks Douglas. I wish they would fix them all.
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
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Re: Full-disk Solar H-alpha Images From GONG
SHOULD BE OF SPECIAL INTEREST TO OUR JAMES.
THANKT FOR SHARING
TERRY
THANKT FOR SHARING
TERRY