A Robotic Wide‐Angle Hα Survey of the Southern Sky

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Abstract
We have completed a robotic wide‐angle imaging survey of the southern sky (δ = +15° to −90°) at 656.3 nm wavelength, the Hα emission line of hydrogen. Each image of the resulting Southern Hα Sky Survey Atlas (SHASSA) covers an area of the sky 13° square at an angular resolution of approximately 08 and reaches a sensitivity level of 2 R (1.2 × 10-17 ergs cm−2 s−1 arcsec−2) pixel−1, corresponding to an emission measure of 4 cm−6 pc and to a brightness temperature for microwave free‐free emission of 12 μK at 30 GHz. Smoothing over several pixels allows features as faint as 0.5 R to be detected.
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