Alluxa 1 A Ca K filter #2

Filter	Test method	f-ratio	Surface  measured	FWHM	BW at 10% peak transmission	delta CWL
	Sol'Ex spectro (fc=fi=200 mm) (IMX 290 or 533)	f-115	10 micron × 4.5 mm	1.40 A	4.1 A	+ 0.40 A at 18°C to 23°C

  

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Low resolution transmission curve

(Ocean Optics HR4000, 0.27 nm/px dispersion


NB : the value of peak transmission on Ca K line is largeley underestimated because of the low spectral resolution.

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Measurement in collimated beam

#1 - Optical set-up:
Sun >> Sol'Ex spectrograph with 10 micron slit : 10 micron × 4 mm. 200 mm f.l. collimating lens (re-focused on Ca K). Grating : 2400 l/mm. 200 mm f.l. imaging lens >> ASI290 camera.
12-bit acquisition. Dispersion: 0.05822 A/pixel.
Blue sky. Temperature: 23°C.
1 September 2023.







The fit with a Lorentzian curve is quite good (one-cavity filter), FWHM = 1.37 A.


#2 - Optical set-up:
Sun >> Sol'Ex spectrograph with 10 micron slit : 10 micron × 4 mm. 200 mm f.l. collimating lens (re-focused on Ca K). Grating : 2400 l/mm. 200 mm f.l. imaging lens >> PO IMX533 camera.
14-bit acquisition. Dispersion: 0.0755 /pixel.
Blue sky. Temperature: 18°C.
13 March 2024.





Fit with a Lorentzian curve , FWHM = 1.45 A.

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#3 - Impact of the tilt of the filter
Optical set-up:
Sun >> Sol'Ex spectrograph with 10 micron slit : 10 micron × 4 mm. 200 mm f.l. collimating lens (re-focused on Ca K). Grating : 2400 l/mm. 200 mm f.l. imaging lens >> PO IMX 533 camera.
14-bit acquisition. Dispersion: 0.0755 A/pixel.
Blue sky. Temperature: 30°C.
25 June 2024.

From top to bottom:
- solar spectrum,
- spectrum with filter at normal incidence,
- spectrum with filter at 1.4° incidence,