[Composite image] Chromospheric/coronal spectra

Composite image of the chromosphere/corona made from the Ha (red), [FeXIV] (green) and HeI (blue) emission lines. The horizontal streaks are continuum emission from the corona.

Slitless spectroscopy results


Slitless spectra were obtained using a Ist order blazed 315 groove/mm transmission diffraction grating fixed in a filter mount on a Hasselblad camera with a 180mm Sonnar and a 2XE converter giving a focal length of 360mm.

chromograph-1.jpg chromograph-4.jpg
chromograph-5.jpg chromograph-6.jpg

The apparatus: 360mm lens with blazed diffraction grating; 1-inch finder aligned to 1st order spectrum.

The limited aperture of the grating meant that the lens was used at approximately f/11. Exposures were calculated from Fred Espenak's tables and multiplied by a factor of 30 to account for the grating dispersion. This factor was determined experimentally by taking Polaroid photographs of a mercury vapour street lamp with and without the grating in place. Between second and third contact, fourteen 6 x 4.5 cm transparency frames were taken on Agfa RSX II 100 ASA emulsion. The exposure times ranged between 1/60 sec and 10 sec. The camera was arranged such that the grating blaze was pointing southeast with the camera axis pointing northwest of the Sun. The chromospheric spectrum seen through the viewfinder was spectacular with the prominences showing strongly in emission. Emission lines could be seen around the whole circumference.

Digital spectroscopy from ESO was obtained by the CAOS group who show a coronal spectrum with Ha, [FeX] and HeI emission lines.

Last update: 30 August 1999: Mail to rfosbury@eso.org
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