Optical longslit spectra of NGC 4410 were obtained on 1991 December 19 - 20 using the Double Spectrograph on the Palomar 5m Hale telescope. In the red channel, a spectrum with a resolution of 2.5 Angstrom and total wavelength coverage of 6340 - 7000 Angstroms was obtained, while the blue spectrum has a resolution of 6 Angstrom and a wavelength range of 3747 - 5250 Angstroms. We made observations at five slit positions in the NGC 4410 system, aligned across the nucleus of NGC 4410A and various knots and features observed in the narrow-band image. Individual exposures were 15 minutes in duration.

The nucleus of NGC 4410A has very broad lines (FWHM ~ 600 km/s). The NGC 4410B nucleus and the filamentary features also appear to have somewhat broad lines (FWHM ~ 400 km/s) compared to those of the knots (FWHM ~ 200 - 300 km/s). Comparison of the observed line ratios with standard diagonostic line-ratio diagrams used to distinguish ionization mechanisms confirms that the bright knots of ionized gas are H II regions. In contrast, the nuclei of the two galaxies fall in the Low Ionization Emission Line Region (LINER) regime. The [N II]6584/H-alpha ratio is high in both nuclei, and the [S II]6717/H-alpha and [O I]6300/H-alpha ratios are enhanced in the NGC 4410A nucleus. The fainter NGC 4410B nucleus is undetected in [S II]6717 and [O I]6300. The northwestern arc also has enhanced [N II]6584/H-alpha, [S II]6717/H-alpha, and [O I]6300/H-alpha ratios, indicating that ionization is dominated by shocks in this region rather than H II regions. The extended gas near the nucleus has line ratios in between these two extremes, indicating that gas from both the nucleus and nearby H II regions contributed to the extracted spectra.