The POISE has an aperture of 80 mm, an effective focal length of 1000 mm, and a field of view of 6.5X6.5 solar radii on a Loral CCD with 2034X2034 pixels. The pixel size is 3.1X3.1 arc seconds. The spectral band of the image is set by an Andover filter with a central wavelength of 620 nm and a bandwidth of 10 nm. The CCD camera is a Pixel Vision Spectra Video camera with 16 bit digitization, an electron well depth of 95,000 electrons, and a read noise 20 electrons. The polarization analyzer contains fixed linear and quarter wave polarizers together with a Meadowlark Optics liquid crystal variable retarder. This image is a calibrated "intensity" composite of a series of 0.25, 1.0 and 4 second exposures.
The POISE98 images can be processed numerically to remove the radial gradient due to the rapid outward decrease in the coronal density. This numerical 'flattening' replaces the radially graded optical filter used in the photographic Newkirk camera which was used in previous HAO eclipse expeditions.
Specifically, the processing involved to produce this image was: dividing a r^-5 filtered, 2-D sobel filtered image, by a r^-5 filtered image. This results in great edge enhancements and discernibility of fine structure in the data.
Such fine details improve understanding of a fundamental solar physics question:
Is is known that most of the heating occurs very close to the solar limb, that is, very low in the corona. And, is only at eclipses where one can observe the corona in this region.
The HAO expedition team for the '98 eclipse is Alice Lecinski, Kim Streander, David Elmore, Greg Card, Bruce Lites, and Steve Tomczyk.
David Elmore developed and perfected the calibration and filtering procedure. Alice Lecinski assisted.
O.R. White provided editting support, and wrote much of the above caption.
R. Lull provided instrumentation support.
The High Altitude Observatory is a division of the U.S. National Center for Atmospheric Research, which is operated by the University Corporation for Atmospheric Research under contract with U.S. National Science Foundation.
