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A Strategy for Improving Image Quality on Kitt Peak (1Dec93) (from KPNO, NOAO Newsletter No. 36, 1 December 1993) As part of our annual exercise of planning improvements to telescopes, instruments, and software on Kitt Peak, we have formulated a strategy aimed at achieving the very best seeing possible at our telescopes. The quality of an image is due to a combination of telescope and instrument optics, atmospheric turbulence and wind shake, and thermal effects within the dome. Recent optical tests of our telescopes suggest that the mirrors are capable of subarcsec images, and yet these are seen only very rarely. Evidence from the Hiltner 2.4-m telescope of MDM observatory on the southwest ridge suggests that the site seeing is frequently that good. One area where efforts to improve image quality may well be fruitful is in the thermal environments of the domes. We have, for some time, been trying to remove heat sources and improve ventilation within all of our domes. We would like to make this a priority for the next few years and determine if the existing telescopes can be retrofited with seeing improvements which will allow them to perform at the site seeing limit. Because the improvement projects at the 4-m are costly, difficult, and lengthy, we must plan to devote a major fraction of our efforts to that telescope. The payoffs there are largest too. We are finishing up an oil cooling system for the oil-pad bearings. We are beginning an engineering study which is preliminary to cutting ventilation holes in the dome next summer. We expect to begin a study this year to learn how we might cool the primary mirror to maintain it at the ambient temperature. At the same time, we would like to make improvements at a telescope where we can see substantial progress in a short time, and so we have decided to try this approach at the 0.9-m. During the coming year, we hope to replace the solid tube with a truss, cut fourteen 4 x 4 foot holes in the dome and install louvered panels, and move all the heat-producing electronics off the observing floor. We will begin thinking about how to cool the mirror here as well. The hope is that after one year and a relatively small investment of resources we will routinely see subarcsec images at this telescope. With the experience gained at the 4-m and the 0.9-m we plan to then move on to the other telescopes. We believe that improving the image quality is very important, both because of the gains in efficiency to be realized from our existing telescopes and because of the way that our instrumentation programs must evolve. In both the IR and the optical, the excitement of the Gemini telescopes comes from the superb image quality expected. Our future instrumentation should take advantage of tip- tilt correction or higher order adaptive optics and should optimally sample the seeing. Now that IR detectors have come on the scene with enough pixels to achieve both good spatial resolution and reasonable field size, we should not be limited by poor telescope images. Similarly, optical spectroscopy stands to gain significantly by using narrower slits. Our program of image improvement is the logical next step in remaining competitive with newer facilities. Todd Boroson
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