| Test method | f-ratio | Surface sampled | FSR | FWHM | Delta CWL | Note | |
| Blocking Filter |
Diode source + collimator + Solex 80 mm / 125 mm / 1200 lpmm / IMX585 | collimated |
7.3 A BW at 10% = 9.7 A |
3-cavity filter 80% peak transmission |
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The free aperture of the Blocking Filter is about 19 mm.
Measurement of the FWHM using the Sun as a light source
Optical setup: Sun => BF => Solex f_c = 80 mm, _fim= 125 mm, 1200 lpmm, IMX585
dispersion = 0.192 A/pixel
The following images show the solar spectrum (without any filter) and the spectrum transmitted by the blocking filter.
We can see that the Center Wavelength of the BF is very close to Ha (at normal incidence).
Transmission is the ratio between incident light and light transmitted by the filter:
The dip at the center of transmission is not a real one. This artifact is the result of the presence of the dark Ha line combined with interpolation effects.
Measurement of the FWHM using a diode as a light source
Optical setup: diode => 5 mm aperture hole => 55 mm f/8 collimator => Blocking Filter => Solex f_c = 80 mm, f_im= 125 mm, 1200 lpmm, IMX585
dispersion = 0.192 A/pixel
The use of a diode as a light source avoids the artefact due to the Ha line when using the Sun as a light source.
Diode source on the left, illuminating a 5 mm aperture hole at the focus of the 55 f/8 collimating lens. Solex spectro on the right.
The measurement of the profile is more accurate than when using the Sun as a light source:
Transmission is measured to about ±5%.
The filter is 3-cavity (BW at 10% peak transmission < 1.5 × FWHM)
Optical setup: diode => 5 mm aperture hole => 55 mm f/8 collimator => Blocking Filter => Solex f_c = 80 mm, f_im= 125 mm, 1200 lpmm, IMX585
dispersion = 0.192 A/pixel
The use of a diode as a light source avoids the artefact due to the Ha line when using the Sun as a light source.
Diode source on the left, illuminating a 5 mm aperture hole at the focus of the 55 f/8 collimating lens. Solex spectro on the right.
The measurement of the profile is more accurate than when using the Sun as a light source:
Transmission is measured to about ±5%.
The filter is 3-cavity (BW at 10% peak transmission < 1.5 × FWHM)