They are ephemeral, lasting a mere 10-20,000 years, a cosmic eye-blink, but thousands are known in our Milky Way galaxy, most extremely faint. However, they are enigmatic, a subject of ongoing research to discover the mechanisms behind their diversity. Tracking them down and discovering their composition and structure by spectroscopy is a fascinating and challenging pursuit and one I find particularly rewarding.
The spectra were obtained primarily for looking at the elemental composition and some images are deliberately overexposed to show the low level constituents. For the larger nebulae, unless otherwise stated, the spectrum obtained is from the slit placed across the centre of the nebula, parallel to the declination axis.
Some of the early spectra are not very good but they get better as my methods improved. Some of the objects are not true planetary nebulae but show similar spectral characteristics.
- Steve Broadbent