We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
1950
TV CAMERA TUBES
241
a frame time, the signal pulse causes the horizontal gating circuit to apply a horizontal centering signal to the tube deflection. The same pulse causes the vertical gating circuit to apply a vertical centering impulse corresponding to the difference in the line number of the actual and prescribed occurrence of the star pulse. To take account of storage, the gating circuits are blanked by the first impulse if, and only if, the latter occurs before the prescribed occurrence of the star pulse.
In speaking of the electronic stabilization of star images to compensate atmospheric disturbances and clock drive errors — a subject discussed last year by Professor Zwicky in Zurich — we have been able to keep our feet on the ground. We shall now contemplate the possibility of placing our telescope in a balloon and ascending to
YOKE .ROTATION
GUIDING / V
„ ACTUAL POSITION
^CORRECTING
\\
TO AMPLIFIER. CONTROL CIRCUITS AND TRANSMITTER
AUXILIARY \ STAR
YOKE
v. PRESCRIBED POSITION
Fig. 15. Image stabilizer for balloon-mounted Schmidt telescope.
heights where atmospheric refraction ceases to play an appreciable role. We will now need electronic methods to maintain the proper orientation of the telescope in spite of the uncontrollable motions of the balloon and, eventually, to send the star images back to earth. Even though this method would not be applicable to the largest telescopes, the possibility of almost completely eliminating atmospheric effects might well render it of value.
We shall again direct our attention to the crucial problem, the stabilization of the sidereal image. As compared with the system for compensating atmospheric fluctuations, we must now count with the possibilities of much greater total displacements and of the 'rotation of the image. We can take account of the first factor by providing servomotors for the rotation of the telscope about a vertical axis and about a tilt axis (Fig. 15). These servomotors are controlled by the centering currents for the scanning pattern. A third servomotor is