Halide reads your numbers off an emission spectrum. Each measurement lands as a bright line at a measured position — so a value is something you locate, not just a digit on a card.
One continuous band runs the width of the page. Bright emission lines mark the figures worth reading; their colour tells you the source. Nothing floats in space — every value sits on the axis.
Open the slit for a measured window and let the source lamp burn its lines into the emulsion.
The continuum resolves into discrete lines. Density tells you which exposures ran hot.
Snap the reading to the brightest line; the value is now anchored to a wavelength, not a guess.
Balmer alpha resolved cleanly against the hydrogen tube standard.
The sodium doublet stays inside the locked window across the full set.
Mercury green sets the calibration baseline for every plate after it.
Bring a data source; leave with a calibrated spectrum where every figure has a place on the line.
Develop a plate