NGC 6543 Cat's eye nebula - Astronomy and astrophotography CCD camera images



17/09/2005
Object name: NGC6543 Cat eye nebula
Popular name: Cat eye nebula
Object type: Planetary Nebula
Magnitude: 8.8
Size: 0.33 0
Position angle: 0
Classification: PN
Apparent RA: 17 58 33.4 Apparent Dec: +66 38 01
Constellation: Draco

The Cat Eye nebula was the first planetary which was spectroscopically investigated and displayed its typical line spectrum, by the English amatuer astronomer William Huggins in 1864. The following table summerises the emission lines I have detected. The spectrum is fairly typical of a planetary nebula showing strong hydrogen balmer emission lines and OIII emission lines. Due to the extended nature of the object, it is not possible to split the two oxygen lines. Also, the Hydrogen Beta line is merged in with the Oxygen. A rather peculiar feature is the emission line at 10049 far into the infra red. Normally such regions are absorbed by the Earth's atmosphere. I noted this line whilst imaging, but put it down to an internal reflection. After analysis it appears to be exactly where the one of the infra red hydrogen emission lines should be. Obviously I am a bit skeptical on that one! The atmospheric absorbtion occours most strongly in particular bands. I note from the reference that there ae strong SIII lines at 9068 and 9531. If the H line is there, then so should these, unless they are being absorbed and the H I is not. Another possibility is some kind of non-linearity in that infra red region - maybe we are infact looking at the SIII.

Another suggestion, from Robin: Its the second order spectrum of the bright OIII line... I am inclined to think this is correct, as I can also see the second order Ha on the original image.

There are possibly some other emission lines between Ar III (7135) and H I (10049) but are too vague to pin down.

4101 H Ep Maybe
4340 H Gam Certain
4861 H Beta Certain - well merged
4958 OIII Certain - merged
5006 OIII Certain - merged
5875 He I Certain
6562 H Al Certain
7065 He I Maybe - bit merged
7135 Ar III Certain - bit merged
10049 H I Uncertain. Suprising in IR

From the same night:
2x Barlow shot
Wide image

Captured in k3ccdtools. Stacked in Registax. Saved as TIFF. Open in photoshop and rotated and cropped. Saved as Tiff. Open in IRIS and saved as FITS. FITS opened in analysed in VSpec. Dispersion = 21.32 /pixel

References: Hyung, S et al


Exposure Details :

StarAnalyser 116x6.2s on 200mm @ F5 with SC3.5

Spectroscopy and vspec tutorial

NGC 7027 - Another spectrum of a planetary nebula

PK 64+ 5.1 Campbell's Hydrogen Star BD+30 3639

Curdridge Observatory, Southampton,UK