Image of the Solar Corona at the 26 February 1998 Eclipse

POISE98 Caption from the HAO expedition to Curacao, Netherlands Antilles


    Image of the solar corona made at the total solar eclipse on
26 February 1998 in Curacao with the HAO Polarimetric Instrument 
for the Solar Eclipse 1998 (POISE98).  This image shows both the 
plumes at the solar poles and the coronal streamers nearer the 
Sun's equator at onset of Solar Cycle 23.

    The POISE has an aperture of 80 mm, an effective focal length of 
1000 mm, and a field of view of 6.56X6.56 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 was recorded with a 1.0 
second exposure time.    

    The POISE98 images are processed numerically to remove the 
radial gradient due to the rapid outward decrease in the coronal density.  
This numerical 'flattening' replaces the radially gradiated optical 
filter used in the photographic Newkirk camera.  In order to improve 
visibility of plumes near the poles and the brighter coronal streamers 
at lower latitudes, the image was also multiplied with a sine^4.0
function in apparent latitude to equalize the plume and streamer 
brightness in this image.    

    The HAO expedition team for the '98 eclipse is Alice Lecinski, 
Kim Streander, David Elmore, Greg Card, Bruce Lites, and Steve Tomczyk.  

    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.


Caption written by Oran R. White, 4/30/98