The photo-multiplier photometers of the Steward Observatory.

Abstract

view Abstract Citations (1) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The photo-multiplier photometers of the Steward Observatory. Carpenter, E. F. ; Wood, F. B. Abstract Replacing the Kunz-type photometer (Photometer A), which was in service through 1947, are two photomultiplier photometers. Photometer B is intended for work of maximum precision on stars of moderate brightness. It is to be used primarily with the ~~-21-inch Xewtonian reflector at the desert station of the Observatory, six miles beyond the Tucson city limits. Customary arrangements provide for interchangeable filters and sky diaphragms. An 840- volt battery supplies potential to the phototube dyn~odes. The anode current is read either directly by galvanometer or, via a direct-current amplifier (after Kron), by a milliammeter or automatic recorder. This photometer is now about to be put into operation. Photometer C is intended to reach the faintest stars p~ssible with maximum stability and versatility. It will be used primarily with the ~6-inch reflector. The mounting of the photometer is exceptionally rigid, to provide for considerable auxiliary apparatus. This photometer is used with the alternating current amplifier described in Gartlein's abstract in this issue. A cylindrical light-chopper surrounding the phototube provides a pulse frequency of 330 cycles per second. Both the amplifier and the phototube are served by regulated power supplies. Direct-current outputs of the amplifier may be taken at 100 microamperes or one milliampere full scale on a Leeds and Xorthrup recorder. An alternating current output can be analyzed with an oscilloscope. Controls of dynode supply and amplifier gains provide full-scale readings over a range of 12 magnitudes. In the lower quarter of the scale the amplifier departs slightly from linearity, but this does not impair linear reductions for bright stars (J mag. 10), where the sky brightness is trivial, or for faint stars, where the sky brightness is substantial. In any case, preliminary tests indicate a fairly stable calibration. This photometer has been in use several months, and it performs with remarkable reliability, steadiness, and convenience. The recorder and all electronic units are on the Xewtonian platform, convenient to the setting ocular. Re- cording is continuous and the observer or his assistant can read and partly reduce the data while the record is being made. Slides were shown to illustrate the stability of the tracings at magnitudes 9, 12, and 14, all of which are of photoelectric precision. The smallest sky diaphragm is 0.5 mm in diameter, corresponding to o~~. With this diaphragm, sky and star deflections are equal at magnitude 15.5, and can be read at full scale. This work has been supported in part by the Office of Xaval Research. Steward Observatory, University of Arizona, Tucson, Ariz. Publication: The Astronomical Journal Pub Date: September 1949 DOI: 10.1086/106252 Bibcode: 1949AJ.....54..182C full text sources ADS |