Antlia 393-3nm filter

Test method f-ratio Surface  measured FWHM BW at 10% peak transmission delta CWL
Sol'Ex spectro
(fi=fc =125 mm)
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 s
lit : 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.

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.


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