In order to ensure that all the spectrosocpes created the same calibration line and equation, one must follow National Institute of Standards and Technology (NIST) standards for comparison.
NIST is authorized to issue certificate for calibration which certifies that the calibration line and equation are upto the standards decided.
How could you ensure that all the spectroscopes created the same calibration line and equation?
Answer: You would simply have to take all the spectroscopes reading and ensure that all the helium lines are recorded in regard with the scale along with their colors and wavelengths. All this data should be graphed on a calibration plot and analyzed.
