www.galaxies.se - by Ivar Hamberg

Spectrum of Comet C/2025 A6 Lemmon. 

This a spectrum taken with my own designed spectrograph using a 300L/mm grating. I used a narrow setting on the adjustable slit, trying to get good resolution. The magnitude of the comet was around 7 at the time of the photo, so I needed to add many exposures to minimize noise. I ended up with 48 shots with 60 sec each. It was somewhat of a challenge to get enough light through the slit. The camera used on the spectrograph is an ASI183M, uncooled.

Date was the morning hours of Oct 12 and 13, 2025.

The Spectrum shows distinct C2 Swan Band lines as well as CN emission and NH2. There is also a possible reflection of H-Beta absorption from the solar spectrum. Na D-lines at 5890-96 are also seen in emission, possibly emitted from the comet core.

At 6300Å and 5677Å I find strong signals, probably airglow! In the photographical spectrum image one can see these lines extending along the whole slit.