Problems began even before they could start observing. The contractor constructing the camera delivered a mirror that didn’t fall within “tolerances,” as opticians call the allowable imperfections. The second cut was spoiled when cleaning fluid spilled on the mirror. Finally, the third cut of the mirror worked. Pennypacker, however, had ordered a camera without a filter, figuring that the more light he got, the better—and not understanding that if you want to compare the brightness of an object on different days, you need to observe in different filters in order to “equalize” the light level.
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