SPECTROSCOPY OF PLANETARY NEBULAE

NGC 2391
NGC 6210
M57 (part one)
M57 (part two)  New (August 8, 2002)

NGC 2391

The image shows the field of planetary nebula NGC 2392 (the Clown nebula) captured with a Jeulin grating (100 lines/mm) placed 21 mm in front ot the surface of KAF-0400 CCD equipping the Audine camera (slitless spectrograph configuration). The telescope is a flat-field camera of 190 mm at F/D=4. The final image represents a stack of ten 2 minutes exposures. The zero order of this one is just on the right center of the image (one may guess the nebular glow). Notice that each star has a spectrum associated. The nebula spectrum is complex: one sees at the same time the spectrum of the central star which is of magnitude 9 approximately and several monochromatic images of the nebula which are superimposed on it. The Jeulin grating concentrates approximately 50% of the signal in the order #0, 40% in the order #1 and 10% in the other orders.

The following figure presents the spectral profile of NGC 2392 extracted from the preceding image. The lines [ OIII ] at 5007 angstroms and Ha at 6563 angstroms are particularly intense. The spectrum shows in fact monochromatic images of the nebula (the "continuum" spectrum of its central star is also visible). The hole in the lines is explained well if one remembers that nebula is a ring and that spectral profile pass roughly by its center.

Spectral profile of nebula NGC 2392.

NGC 6210

The nebula NGC 6210 observed with the 190-mm telescope and a Rainbow Optics grating of 200 lines/mm (April, 24, 1999). We favorise here luminosity rather than the spectral resolution. Thus, the grating is placed very close to the CCD: 13.4 mm in front of it. This was possible with Audine camera by placing the grating even inside the box of the camera. Dispersion is of 32 A/mm approximately.

Spectral profile of NGC 6210 captured with the grating Rainbow Optics.

Detail on the weak emission lines of NGC 6210. The use of CCC KAF-0401E, by its great sensitivity in blue, made possible the detection of  the line [OII] at 3738 A.

M57 (part one)

Slitless high resolution observation of the famous Messier 57 :

The spectrum of nebula M57 in the vicinity of line Ha captured Aug'99 with at the resolution of 3000 approximately. Sampling is of  0.93 A/pixel. Co-adding of 17 images, 120 seconds exposures each. This document shows that line Ha is not the only source of light in this area of the planetary nebula spectra. This one is surrounded by the lines [NII], which still are more intense. The line at 6364 angstroms is [OI]. For a peculiar processing description of this image, click here.

Spectrum of M57 for the green. Note the small size of the nebula at 4686 angstroms He II line (only the central part emit at this wavelength).

M57 (part two)

Commented 2D spectrum of M57 (exposure: 18 x 120 seconds - Instrument: Takahashi FS128 refractor (5-inch aperture) + 2.88 A/pixel slit spectrograph + Audine CCD camera Kodak KAF-0401E) : this spectrum show lines of my light-polluted site (yellow), airglow lines of the atmosphere (green) and M57's lines (red). For detail related to the night sky spectrum, click here. Note change of morphology of the nebulae relative to the spectral line. Note also the simultaneous [OI] 6300 A presence in the terrestrial atmosphere and in M57 :
 

Slitless 2D spectrum of M57 with the same instrument. Note the broadening of the high-pressure sodium and mercury street lamp lines and the blend of the M57 lines (i.e. lower spectral resolution):