NGC 7635 spectrum

Instrument : Celestron 11 (D = 0.28 m) + LISA spectrograph (click here for technical informations) at R = 800 + Atik 324L+ CCD camera
Observatory : Castanet-Tolosan
Observer : Christian Buil
Exposure : 9 x 300 s (Oct. 15, 2011)
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2D spectra of NGC 7635 region (two slit position - 35 microns wide).

Spectral change function of considered nebula zone.

Method for isolate the spectrum (double exposure - one directed on the nebula, one directed outside the nebula, then subtraction of the two shots). The acqusition are doing in a severe light pollution suburban conditions.
Note the signal to noise ration degradation at the level of intense parasitic spectral zone (photon noise) - but a  spectrograph is very efficient for observe under hard condition (Halpha, [OIII], ... spectral signature are well preserved).