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

• A 1/15s exposure taken some 15s after 2^nd contact. This is unprocessed and shows the uneven response of the photographic film with minima in the yellow and blue-green. The rings are images in the chromospheric and coronal emission lines and the streaks are the continuous emission from the corona.
• Montage of nine spectra with exposure times from 1/60s to 10s. The first was taken shortly after second contact and the last at third contact. The dominant emission lines are the Balmer series from H-alpha to H-delta and the Helium D₃ line at 5876A. The two strong coronal lines [FeXIV] 5303 and [FeX] 6374 can be seen with a different spatial distribution. In the spectrum taken just before third contact, several other Fraunhofer lines (NaI D-lines and the MgI triplet) can be seen in emission.
• An enlargement of the red (1/2 sec) and blue (1 sec) exposures taken approximately in mid-eclipse. These are labeled with the hydrogen, helium, iron and calcium lines which are clearly visible. The calcium H and K lines are in a region where the lens focus is not perfect. Note the high prominence to the west (right) seen clearly in Ha and D₃. The chromospheric (hydrogen, helium, calcium) and coronal (iron) emission lines have quite different spatial distributions.
• A combination of the spectral enlargement with a direct image taken at 3^rd contact by Philippe Duhoux from a site NW of Munich. The prominences and the bright low coronal regions can be easily identified. A second combination - including the CCD coronal image taken in France at Vouzier (Champagne-Ardennes) by Cyril Cavadore from ESO and L.Bernasconi and B. Gaillard from Obs. de la Cote d'Azur. Both of the direct images are available at the ESO eclipse report website.
• A composite colour image is shown at the top of this page. It was constructed by selecting images in Ha, [FeXIV] and HeI from early in totality, aligning them and then placing them into the R G and B planes respectively of a Photoshop image. Some image manipulation was done to reduce the effect of the coronal continuum which produces the horizontal streaks. The green coronal line can be seen extending along the whole of the western limb and is very strong in a region to the east. An alternative composite made from HeI (red), [FeXIV] (green) and H-beta (blue) gives somewhat better resolution and shows the greater height of the western prominence in the helium line. An image montage containing this second composite, an Ha image (No. 6) and the Cavadore and Duhoux images at the same scale and orientation has been constructed (1024 x 1024 jpg).
• Sequence of Ha images (top to bottom) during the second half of totality running until just before third contact. This shows the evolution of the western part of the chromosphere including a high prominence.
• Sequence of 13 Ha images made into a looping movie. The exposure times were different but some attempt has been made to equalise the intensities. The last two frames show the low chromosphere and then the photosphere emerging at 3^rd contact. The [FeX] coronal line can be seen on the left in the middle of the sequence. Here is a larger 512sq version. [Frame No. 7 is saturated in Ha and so not included in the sequence.]
• Descriptions of individual spectra.
• List of emission lines seen in two of the prominences (S and NW) and the flash spectrum from the W limb just before third contact: as an Excel workbook (.xls) and as sylk.

Method

Slitless spectra were obtained using a I^st 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.

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