DayStar PE 0.6A#2

The filter was measured using interferometry with an Ha lamp and diffused light.

Filter Test method f-ratio Surface  measured FSR FWHM
DayStar PE 0.6A#2 Ha lamp collimated Full aperture
26.4 A
(asssuming a 1.575 index for mica)
0.95 A

Measurement of the etalon with a Ha lamp

Nikon Z6 with Nikkor 50 mm S f/1.8 lens at f/2 - center of the etalon - 20 s exposure - 800 ISO - 17 September 2023 - etalon at operation temperature.

Etalon gap index :
The main assumption to be made in the measurement with a Ha lamp is about the index of the mica gap. A value of 1.575 is assumed (same value found by spectrometer on other mica-spaced etalons).

The resulting FSR is 26.4.

On this basis, the average value of FWHM measured over the full diameter of the etalon is 0.95 A (collimated beam).

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