| Test method | f-ratio | Surface measured | FWHM | BW at 10% peak transmission | delta CWL |
| Sol'Ex spectro (fi=fc =125 mm) (fi=fc=200mm) |
f-115 |
10 micron × 4.5 mm | 3.6 nm | 4.8 nm | + 0.4 nm (at 4°C and 14°C) |
Measurement in collimated beam
Optical set-up:
Sun => Sol'Ex spectrograph with 10 micron slit : 10 micron × 4 mm. 125 mm f.l. collimating lens (re-focused on Ca K). Grating : 2400 l/mm. 125 mm f.l. imaging lens. ASI290 camera.
12-bit acquisition. Dispersion: 0.0932 A/pixel.
Sun at low elevation (20°). Temperature: 4°C.
12 December 2022.
The filter is exposed to nearly perfect collimated light beam: converging light beam with a 0.5° cone (solar disk), equivalent to f-115 ratio. The surface of the filter sampled is set by the slit size (10 micron x 4 mm)
The following three images show:
- the solar spectrum near Ca K and H,
- the spectrum transmitted by the Antlia 393-3 nm at normal incidence.
- the solar spectrum near Ca K and H,
- the spectrum transmitted by the Antlia 393-3 nm at normal incidence.
Transmission profile at normal incidence in collimated beam
Same results were obtained with the Sol'Ex V2 (and improved spectral resolution) :
The saddle at 393.3 nm near peak transmission and various secondary dips are artefacts.