wpo - colourful spectra via drift method

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These shots are via my Canon Rebel =300D DSLR with a Rainbow Optics transmission grating in the convergent beam of an undriven 4" Meade SCT allowing the star and its spectrum to drift across the field in typically 20 seconds exposure.  The spectrum of zero mag star Vega has had no enhancement in colour and contrast and fairly indicates the colour representation and spectral range for the Canon CMOS detector - something rarely provided for by manufacturers.  Other stars include alpha Oph [A-type] and orange/red stars alpha Boo + beta Peg [K-type] and alpha ,

+ 17mm fl f/4 lens + BDB IR transmitting filter and cover a ~10o x 7o field.   The filter appears black eg visually opaque but most astro-CCDs have good sensitivity to these wavelengths.  The setup is piggybacked on my Meade LX200 and was prompted by the current [Aug 06] rare ~mv 3.8 brightness of chi Cygni that S&T's John Bortle quotes "as the brightest for 148 years" and the brightest star in Cygnus at IR wavelengths! - see S&T's homepage for my IR Cygnus image.

Most of the recorded stars, beyond the brightest, prove to be visually faint red stars of spectral class K and M - chi Cyg is an M variant at type S - its spectrum with beta 1+2 Cyg [=Albireo] for comparison is shown adjacent.

More recent shots include Lyra in both visual and IR highlighting stellar magnitude differences and Delphinus + Sagitta in IR. All these shots processed to remove background and just hi-light the stars except Aquila/Scutum 10min shot of the Milky Way in IR light.

Here is a list of bright red stars and faint red stars eg mostly M-type and carbon stars but with some exceptions.



images& text copyright Maurice Gavin 2006  visitors