However video also has advantages for measuring slow moving objects such as comets and asteroids that move less than an arc sec per minute. For fast moving objects (having a speed of say more than a few arc sec a minute) video is the natural choiceįor astrometry because of it's very fine time resolution - 0.04 sec. With video we can do astrometry on two types of objects - fast moving and slow moving. And remember that the telescope is only part of the equation and for good astrometry you need a good integrating video camera and at least a few tens of reference stars in your fields. You should do your own tests to determine the accuracy of Tangra for your optical system before you do any serious astrometry. The observations were made with a SCT which has a very small field distortion. While the results are satisfactory (75% of the reported positions of asteroids with well known orbits were with residuals of 0.3" or better and 100% of the reported position were with residuals better than 1") The astrometric residuals of these observations reported to MPC are available. During the prototyping phase a number of astrometric positions of asteroids in the range of 12 - 14 mag have been taken with an 8" SCT and WAT-120N+ video camera, have been reduced with Tangra and the positions reported to MPC. In fact video astrometry was the driving force for the whole project to commence. (See also Step-by-Step Astrometry Reduction Examples)Īstrometry was an important part of the prototype of Tangra built in the middle of 2009.
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