Full-Disk Solar Hα Images from GONG J. Harvey, J. Bolding, R. Clark, D. Hauth, F. Hill, R. Kroll, G. Luis, N. Mills, T. Purdy (NSO), C. Henney (USAF AFRL), D. Holland (Cobham), J. Winter (Daystar Filters) Filter CCD Camera Lenses Light Baffle Beam Splitter Fold mirror Lens Filter CCD Camera Main Points • Full-disk Hα imaging added in mid-2010 to all six GONG sites • ~90% coverage at one image per minute • Backup for forthcoming ISOON network • Funded by U.S. Air Force Weather Agency • Data archived for research • Images available within a minute for real-time work The System • Separate, non-interfering addition to normal GONG helioseismology system • After preliminary processing, images are compressed and sent to a cloud server • Reduction is completed and images are normally available within a minute after exposure The Instrument • Uses GONG light feed and 7 cm objective lens • Polarizing beam splitter diverts otherwise unused 656 nm light through two afocalizing lenses • Daystar 0.04 nm passband mica etalon filter aperture matched to GONG entrance pupil • Following Galilean telescope forms a solar image on a DVC 2k x 2k interline CCD camera • Automatic adjustment of exposure time to keep quiet disk center at 20% of dynamic range • Image resolution limited by diffraction, seeing and high-order wavefront errors in the filters • Unique dual-heater system developed by Daystar to homogenize the passband properties Data and Access • In regular use for space weather forecasting by U.S. Air Force Weather Agency • Operational and reduction improvements underway • Archived data being used in research projects • Access at http://halpha.nso.edu . Main page shown to the right. Sample Observations • Below are sample images of various events extracted from archived data • Image scale is identical for all images (75 arc sec per inch) • Most images sharpened with a wavelet filter and saturated at ½ full range • Movies are available in the archive and at the gallery X-Class Flares M-Class Flares Post-Flare Loops Dark Prominence “Bubble” M Flare + Moreton Wave 2011 03 16 22h 2011 02 28 13h 2011 03 07 14h 2011 03 14 19h 2011 02 15 02h 2011 03 09 23h 2011 02 14 17h M-Class Flares with Surges 2011 04 22 16h 2011 04 22 05h 2011 04 15 17h 2011 03 24 18h 2010 08 07 18h 2011 02 16 14h 1 min running difference 2010 11 20 21h No filter, ¾ dynamic range 2011 03 16 23h