wpo - Minolta D7 digital camera -  stellar spectra

These are sample stellar spectra taken through cloud gaps via a 30^o prism Sellotaped into the lenshood.  Typical exposures 30s at full aperture [14mm diameter] and full zoom [200mm efl] or 400mm efl [plus x2 digital zoom] on auto [~150 ISO]  from a static tripod.  For some stars to the east [Vega] or west [Jupiter] the prism was rotated clockwise/ anticlockwise via the lenshood thread so the diurnal motion trailing the stars was approximately at right angles to dispersion.

Stars include Vega, Arcturus, Spica, Regulus, planet Jupiter and wide-field shot of Lyra..

Piggybacked camera under Megastar control: A second series taken with the camera prism combo piggybacked on my equatorially driven Meade LX200 SCT for improved stellar penetration and spectral information eg line structure.   Stars included are A-type Vega with Balmer series of hydrogen lines, K-type Arcturus and M-type Rasalgethi [alpha Bootis], delta2 Lyrae - latter pair show absorption bands.  Wide-field shot of Corona Borealis down to mag ~6.

The telescope autoslewed onto the target star via a mouse click on the Megastar screen controlling the telescope.  Due to prismatic deviation of the camera's view [half the prism's 30^o wedge angle] the telescope reset ~15^o degrees in declination below the normal pointing angle to centre the star.

Moonlight neutralizes sodium skyglow!   During the sequence of spectra taken May 13 [below] a due south near full gibbous moon illuminated the sky with a diffuse blue 'daylight' glow which appears to neutralizes the typical sodium skyglow.   Normally RGB correction needed for a neutral sky colour.

Some general conclusion about digicam spectra.  This series of mainly variable stars with M-type spectra.   Only A-type stars with strong Balmer hydrogen lines record and M-type stars the fluted molecular bands although artefacts start to appear due to underexposure/ undersampling below mag 3.  Remaining stars eg hot O/B or cooler F/G/K types record virtually no absorption lines.  A rare exception is P Cygni [2 pics] with strong Ha in emission just recorded.