WPO
- widefield images via Canon 300D DSLR
my spectroscopy.....more
Canon 300D shots
2005
Aug: Cropped shot of Cygnus field below
taken with a 30o prism set in a lenshood before 85mm fl f/2 lens goes down
to ~ mag 8. The stars are all dispersed into tiny spectra.
Marked Wolf-Rayet [WR] stars are exceptionally 'hot' with emission lines
especially in blue that the Canon 300D records very well. The 'permanent
nova' P Cygni and a 'cool' Carbon star [without blue in its spectrum] and
other variables are also highlighted together with M57 [weak Ha
+ strong OIII emission] and M13 globular [continuum].
The camera is piggybacked on my LX200 SCT [any
suitable tracking system will do] and the camera rotated ~15o [half the
prism angle] so the view in the centre of the camera viewfinder coincides
with the telescope finder crosswires to aid pointing at selected starfields
to be recorded.
The principle advantage of an Objective Prism,
as it's called, is all the dispersed light forms the spectrum [with a grating
only a percentage of the light forms the primary spectrum] but conversely
the prism [unlike the grating] has no immediate reference to calibrate
for wavelength. Try Edmund
Scientific or Surplus Shed
for prisms.
2005 July: some tracked Canon 300D shots with 135mm f/2.8 Pentax screw lens attached via Kood Pentax screw/Canon EOS adapter.
Original 6Mb images flat-fielded / reduced to 25% full-frame size / mild USM / 20% JPG compression / record ~40 stars/degree to ~m11 in 30s exp.
Note that the original sample [top left insert] resolves the ring structure of planetary nebula M57 etc and good star images to corners of 10o x 7o field.
By boosting colour saturation 200% and extracting R/B channels [shown as negatives] stellar colour indexing [=broad spectral type] may be deduced by measuring the relative R/B intensity of each stars as highlighted below. Many variable stars down to mag 10 identified but not shown here.
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