IMAGING CORONAL EMISSION-LINES UNDER HIGH SKY-BACKGROUND CONDITIONS

We have obtained images in solar coronal emission lines under high sky -background conditions by making precise differential measurements bet ween the coronal emission line and the near-by continuum, which is pri marily due to scattered light from the solar disk. Chopping between th e two wavelengths was performed at 100 kHz to avoid artifacts from fas t-flying dust particles and other aerosols, and also from seeing effec ts. The differential signal was detected with a novel CCD camera that demodulates signals up to 100 kHz. These preliminary observations show coronal emission at the 0.2% level of the scattered-light background and pave the way to efficient and precise imaging of coronal emission features under less than ideal 'coronal-sky' conditions.