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I 38303 Preliminary measures with microphotometer

x and y are reckoned film up. x is R.A. 
Setting for position made by centering the red spot on H gamma.
Settings on spectra made with the spot tangent to and to the violet of the hydrogen lines*
Spectrum 1 is ringed with red on the plate, which is placed in the machine N down

*this is a provisional and admittedly inaccurate method of setting for a first trial

The spectra are identified from the measured x and y coordinates by laying the plate on a réseau squared in cm (the unit in which x and y are measured), adjusting so that the marked spectrum No.1 is at the right position, and [[strikethrough]]reading[[/strikethrough]] finding the other spectra from the measured coordinates. Simultaneously the corresponding stars are located from a similar plate, with a chart.
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