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We consider the use of the commercially available Fabry-Perot etalons (FP)for the imaging of the solar chromosphere in the H alpha line of HI. Threeetalons of 40, 60 and 90 mm diameter were accurately analysed. At normalincidence the maximum transmission wavelength as well as the finesse wereevaluated. Polynomial curves precisely fitting the transmitted centralwavelength variations when using a quasi-parallel beam from a point-like sourceare presented. Further calibrations have been done with photometric accuracyusing a laboratory set-up comprising i/ a 16 bits CCD camera; ii/ a Littrowspectrograph of a spectral power 110000 giving a linear dispersion of 0.0058nm/pixel and iii/ an artificial Sun used as a light source and iv/ preciselyadjustable in position optical components, including the F-P etalons. Inaddition, a precise laboratory wavelength calibration was performed using a lowpressure deuterium 2D spectral lamp simultaneously illuminating the adjustableentrance slit using a splitter before. The variations of the FWHM of thespectral transmission variations as a function of the incidence angle of aparallel beam are also given for each etalon. Consequences resulting from theuse of a low but significant aperture/ratio are tentatively discussed for thefirst time. An application to a precise photometric work of solar physicsinterest when using limb filtergrams is illustrated and discussed, withemphasis on the photometric accuracy resulting from the use of such etalons putbefore the entrance aperture of an imaging telescope. Monochromatic images ofthe solar chromosphere shell in the vicinity of the polar and equatorial limbswere made using a small telescope, in order to deduce the variation of thetypical average thicknesses at poles and equator interpreted as a prolatenesseffect of the chromospheric shell observed during the last minimum of solaractivity (2009).

Photometric properties of new solar H alpha commercial Fabry-Perot etalons. Application to the analysis of the chromospheric fringe