Let me explain the title. At the observatory we were discussing how to get some real scientific measurements out of our telescope. It so happened that our expert former-professional astronomer and author member was there and he suggested that we could record the spectra of stars. For this purpose, we have a cardboard circular attachment with what looks like tights material streched over it, which velcros onto the front of the telescope. This is actually a clever but rudimentary diffraction grating that splits some of the light from stars into spectra that radiate out from them. We spent a while looking at bright stars and seeing rainbow starbursts all around them! However, we couldn't make out any colours in the outer spectra as they were just too dark. Our former-pro must have had unique eyes as he could see colour all the way out. At this point I got rather inspired, as I had once looked at a mysterious object called "Campbell's Hydrogen Star". It was an ordinary star to me at the time, except that it didn't disappear when I put a nebula filter in the eyepiece. Here is an image of that object (147"@ISO1600, f=2400mm f/4.8) and its spectrum which I have specially processed by cloning the image, rotating 180º & excluding anything that didn't match, thus highlighting only the spectrum of the object.Campbell's star is a bright (9m) but very small (5") planetary nebula 2.5º north of the star Albireo, that went undiscovered until the invention of the spectroscope. It has a strong emission of hydrogen lines (see the red, blue, violet bands in the spectrum). Also there is some emission in the middle of the spectrum, presumably from the central star (11m). Maybe a messy picture, but pretty good for a pair of tights.
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