Overall results

	Test method	f-ratio	Surface sampled	FSR	FWHM	Delta CWL	Note
Lunt 40 mm (#4)	Ha lamp	collimated	full aperture 15 mm diameter	12.0 A 12.0 A	0.64 A 0.63 A	+ 0.21 A + 0.28 A

The transmission curve of the etalon is a textbook Lorentzian.

Test of the etalon with the Ha lamp in diffuse light

Optical setup: Ha lamp => diffuser => etalon => Nikon Z7II with 85 mmS f/1.8 lens


Interference fringe pattern

Lunt LS40FHa - Interference fringe pattern - Nikon Z7II - 85 mm S f/1.8 Nikkor lens at f/2.0 (i.e. 40 mm aperture) - 12-bit RAW file - 0.25 s - 100 ISO - 17 January 2025

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