Altair

Last month I tried a few different ideas with my Star Analyser diffraction grating. One of the bigger successes was taking some black and white images as well as the usual colour shots. Since it's usually best to experiment on something that's easy to find and that this was still summertime, I settled on Altair.

Altair is one of our near neighbours, about twice the mass of the Sun and ten times as luminous. Similarly to the other two points of the summer triangle, Altair is of spectral class A so has some fairly strong Balmer lines that should show up nicely using the Star Analyser. Here's what I ended up with:


Both sets of spectra have their merits but the black and white trio show much more detail. The colour pictures show a clear H-Beta absorption line (in the light blue) but the H-Alpha and H-Gamma lines (in red and blue, respectively) have to be searched for. The black and white shots not only clearly show these three absorption lines, but also show the H-Delta line.

It is also much easier to locate the peak luminosity when looking at the black and white images. Looking at the colour images the peak luminosity could lie anywhere in the light blue, green or yellow. The black and white images quite clearly show luminosity peaking in yellow.