WORKING AND USE

The Meade LX200 Field De-Rotater

The working of the Field De-Rotater is very very simple. As shown on the picture, it is composed of a big box, provided in the front of a female thread of screw and male thread of screw to the rear. This box contains an electronic and mechanical system with a step-by-step motor.

Field De-Rotater possesses, on its flank a RS232 connector. It must be connected with the cable, supplied, to the RS232 connector of the LX200 control panel. By this way the LX200 digital computer will supply the FDR and to pilot it. To correct the effects of field rotation, the LX200 computer will induce a counter-rotation of the rear part of the FDR with all accessories. The other part of the FDR stays fixed. This counter-rotation is realized by the step-by-step motor of the FDR. The speed of the motor is determined and is piloted by the LX200 computer according to the position of the telescope. The LX200 computer modifies, instantaneously, and automatically, the speed of the counter-rotation when the telescope follows the object in the sky or when the amateur slew to a new object.

.................................The Field De-Rotater and its RS232 connector..............................                                             Field De-Rotater and its RS232 cable

So all happens as if the telescope was in polar alignment, except that it is in altazimuth mode. And a large number of applications can be achieved in CCD imaging.

The use in the field becomes very easy. Once the LX200 put in altazimuth mode on its tripod and leveled, it is necessary to screw the FDR on the tube. Then, we install behind the FDR the different accessories, as focal reducer and CCD camera. In my case the CCD ST-9E is connected to the CCD connector of the LX200 and the FDR to the RS232 connector. Once ready, you can turn on the LX200, the FDR will emit 4 beeps to indicate it does the link with the LX200 digital computer. Then it remains to follow the classic procedure of 2 stars method. So, the LX200 will determine the speed of correction of the FDR. That's all, you can check collimation and begin CCD exposures.

My old ST-9E on the Field De-Rotater

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