The Spectrum of C/2023 A3 Indicates a Depleted Composition

Abstract We report a spectroscopic observation of comet C/2023 A3 using an 80 mm apochromatic refractor equipped with a custom-built spectrometer with a resolution of R ∼ 2500 on the night of 2024 October 4. Sodium D lines were detected prominently, while no other emission lines, particularly carbon-bearing species, were observed, which suggests that comet C/2023 A3 may be carbon-depleted. The mobility and flexibility of our observational setup highlight the value of amateur telescopes in observing low-altitude targets like C/2023 A3 as a complement to professional facilities.