The various instrumental sources of error in astronomical photoelectric photometry are discussed from a theoretical standpoint. Methods of constructing photoelectric photometers fOr maximum per- formance are suggested, and the ultimate performance limits attainable with presently available com- ponents are discussed. The largest available resistors (1013 ohms) should be used for the photoelectric-cell load-resistor in order to obtain the most favorable signal-to-noise ratio. With a 1O~-ohm resistor, a gas multiplication in the photoelectric cell of 3.5 is sufficient to extend the limiting magnitude to the point at which the cell begins to limit the precision of measure. The photoelectric-cell limit for a cell having the antimony- caesium surface (such as the 1P21 electron-multiplier phototube) is abo~it magnitude 11.3 with a 12- inch refracting telescope while, if sufficient multiplication is used in the cell, it should be possible, a!- though with less precision, to reach magnitude 16.3 with a 12-inch telescope
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Harold L. Johnson (1948) studied this question.