1999 June 7 - comparison spectra of Arcturus [K2 III] and semi-irregular
variable - V Boo [M6e].
The Long Period Variable [LPV] star Mira [o Ceti] near maximum light in 1998 Oct. A 'cool' star, of M-type spectra, it's able to support molecules like titanium oxide [TiO] in its atmosphere which gives the characteristic 'fluted' appearance to the spectrum. Most of its radiation is in near-infrared and although an IR block filter used the star largely ignores it as shown by the bright peak to the extreme right ! There is no 'colour' beyond the visible range so although the camera will record IR it shows as a false pale green.
Spectrum of the classic Mira variable - R Leo - near minimum light of m11. Snapped in 17 seconds exposure through a brief cloud gap, a star of this type fades from visibility because there is a shift in the dominant radiation towards infra-red. Wavelengths are marked on the image.
Spectra of two M- type stars i.e. Wolf 359 [CN Leo] - third nearest star to solar system and T CrB [recurrent nova]. Both spectra are very complex and may show hydrogen lines in emission. Arcturus [alpha Boo] and Denebola [beta Leo] used for comparison.
