“Have you guessed the worst of it? I compute that the sun can probably be moved. The sun can be made to jet plasma, and the plasma can be made to act as a gas laser, forming a photon drive for the sun itself. The Ringworld would be pulled along by the sun's gravity. But even the maximum thrust would be minuscule, too little to help us. At anything over two times ten to the minus fourth power gravities of acceleration, the Ringworld would be left behind. In any case, radiation from the plasma jet would ruin the ecology. Louis, are you laughing?”
Louis was. “I never thought of moving the sun. I never would have. You actually went ahead and worked out the math?”
Wintry-cool and mechanical, that voice. “I did. It can't help us. What is left?”
-- Larry Niven, The Ringworld Engineers
Two guiding modes are available: Gyro Hold, and Fine Lock. Fine Lock (PCS MODE FINE) is used by default, since use of Coarse Track may be harmful to the Fine Guidance Sensors. Use of Gyro Hold (PCS MODE GYRO) is not generally recommended, even for snapshot (SNAP) observations, since the pointing accuracy is only 14". Also the drift rate is 0.0014" s-1 so exposures >100s can result in smeared images. However, if the reduced pointing accuracy can be tolerated, and the exposures are only a few seconds or less, Gyro Hold can give a significant savings in the target acquisition overhead time.
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