Spectroscopic completeness vs. r-band Petrosian magnitude in SDSS DR18 (green dots) and NSA (red crosses) and their combination (blue diamonds). The vertical line at r_petro = 17.77 shows the magnitude selection limit for the SDSS spectroscopic sample. The spectroscopic completeness was computed as the number of galaxies with spectra in SDSS or NSA respectively, over the number of galaxies with photometry in SDSS DR18 within a 300″radius of each galaxy of our sample.