A method is provided for characterizing luminous celestial objects (e.g., stars) in celestial navigation of a missile system. The method includes segmenting, assigning, measuring, computing, ratioing, producing, scaling, and determining operations. Segmenting includes subdividing wavelength range into discrete contiguous bins. Assigning arranges each bin into a plurality of color bands. Establishing sets a transmissivity to each bin of each color band. Computing calculates broad-based fluxes for a reference value as a reference flux. Ratioing computes a ratio between the target flux to the library flux as a color scale for each band. Squaring determines the library flux for each band as a library flux squared. Producing sums a spectral scale over the color bands, a second multiplication of the color scale and the library flux squared as a first sum product, and sums over all the bands the library flux squared as a second sum product and dividing the sum products. Scaling factors each measured intensity of the measured intensities as a scaled intensity by multiplying each target intensity by the spectral scale for each bin. Determining sums a scaled broad-band flux for each band over the bins, a third multiplication of the transmissivity and the scaled intensity.