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Ring images

Ring images are what they say, images of the ring pattern produced by the arc lamp. Use the same setup of the calibration system as is used for the phase-calibration cube, and select one plane which shows a nice ring pattern. Obtain a 2D image of this ring pattern every hour or two throughout the night.

By tracking variations in the radius of the ring through the night it is possible to monitor and correct for drifts in the etalon gap. By tracking variations in the coordinates of the centre of the ring pattern, it is possible to monitor and correct for flexure


Thu Apr 7 00:29:52 BST 1994