Coronado SM60 Gen I

Overall results

	Test method	f-ratio	Surface sampled	FSR	FWHM	Delta CWL	Note
Coronado SM 60 Gen I	Ha lamp	collimated	full aperture	9.8 A	0.67 A	+ 0.48 A	a 0.69° tilt is required to compensate the 0.48 A CWL offset

The transmission curve of the etalon is a textbook Lorentzian.

Additonal result : gap = 0.22 mm

Test of the etalon with the Ha lamp in diffuse light

Optical setup: Ha lamp => diffuser => etalon => Nikon Z7 with Sigma Art 135 mm f/1.8 lens at f/2

Interference fringe pattern

Coronado SM60 Gen I - Interference fringe pattern - Nikon Z7II - 135 mm f/1.8 Sigma lens at f/2.0 (i.e. 66.3 mm aperture) - 14-bit RAW file - 0.77 s - 100 ISO - 10 August 2025

Comments:

- The interference patern is quite uniform with a nice Lorentzian profile for the rings.
- The mesurements from the different rings are very consistent.
- There is a slight increase in the CWL offset (about +30% estimated visually) close to the outer rim of the etalon, and to a lesser extent close to the central spacer. This is taken into account in the measurement which is integrate over the full-aperture of the etalon.