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T. E. Holzer, H. R. Gilbert, D. F. Elmore (NCAR/HAO), R. M. MacQueen (Rhodes College)
A new method for determining line-of-sight velocity has been developed for the MLSO/CHIP He I 1083 nm instrument. The method involves tuning the Lyot-type spectral filter to seven different positions during each observing sequence (lasting about 3 minutes). The algorithm for line-of-sight velocity determination using these seven filter positions yields an accuracy of better than 10 km/s over a line-of-sight velocity range from –100 km/s to +100 km/s. The method is applicable to the observation of filaments, surges, sprays, and other features exhibiting sufficiently strong absorption or emission in the 1083 nm line. It therefore will be particularly useful in the study of eruptive events seen against the solar disk, such as filament eruptions associated with earthward-directed coronal mass ejections.
The High Altitude Observatory (HAO) is part of the National Center for Atmospheric Research (NCAR), which is sponsored by the National Science Foundation under the management of the University Corporation for Atmospheric Research.