Solar Ca K and Ha filters testing

Objectives

- get a qualitative estimation of the filter uniformity (CWL) accross its full aperture,
- get a quantitative estimation of the FWHM and FSR of the filter.

Methodology

Three complementary approaches are used depending on the type of filter.

Test in diffuse light using a Ha lamp Ha etalon only Measurement of the average FWHM, delta CWL over the full (or a sub-) aperture of the etalon.
Nominal values are measured (i.e. in a collimated beam).
Measurement of the etalon non uniformity (CWL drift).
Description and associated procedure
Test with Sol'Ex spectrometer Any filters Measurement of the FWHM, delta CWL over a 10 micron x 4.5 mm surface of the filter.
Measured in a collimated beam (f/115) or with the telescope set-up (i.e. telecentric beam at f/27.5 or f/35, double-stacked, etc.).
Some notes on Sol'Ex
Test in a collimated beam and Ha lamp Ha etalon only Qualitative assessement of the uniformity of the filter over its full aperture. Description and examples


Air-spaced Ha filters

Filter Test method f-ratio Surface  measured FSR FWHM delta CWL Notes
Coronado PST etalon #1
Ha lamp collimated Full aperture 9.3 A 0.61 A with PST tuned to Ha line at f-35
Sol'Ex spectro f-115
f-35 telecentric
f-27.5 telecentric
10 micron × 4.5 mm 9.3 A 0.34 A
0.76 A
0.93 A
with PST tuned to Ha at f-35
with PST tuned to Ha line at f-35
PST tuned to Ha line at f-27.5
Coronado PST etalon #2
Ha lamp collimated Full aperture 6.9 A 0.98 A with PST tuned to Ha line at f-35
Sol'Ex spectro f-115
f-35 telecentric
f-27.5 telecentric
10 micron × 4.5 mm 6.9 A 0.40 A
0.71 A
1.01 A
with PST tuned to Ha line at f-35
with PST tuned to Ha line at f-35
PST tuned to Ha line at f-27.5
Coronado SM40 #1
Ha lamp collimated Full aperture 12.1 A 0.74 A negligeable
Coronado SM40 #2
Ha lamp collimated Full aperture 11.9 A 0.95 A 0.85 A
Coronado SM40 #2 BF5 diagonal Sol'Ex spectro f-14.4 10 micron × 4.5 mm 6.9 A +1.5 A 2-cavity filter
Coronado SM III 60 mm tilt
and 60 mm Rich View etalons
Ha lamp collimated Full aperture 8.5 A
8.9 A
< 0.55 A
< 0.58 A
from 0.55 A (center) to 0.60 A (at 25 mm from etalon center)
from 1.20 A (center) to 1.25 A (at 20 mm from etalon center)

Mica-spaced Ha filters

Filter Test method f-ratio Surface  measured FSR FWHM
Quark (chromosphere version)  #1 Sol'Ex f/45 telecentric 10 micron × 4.5 mm 40 A ? 1.0A


Ca K filters:

Filter Test method f-ratio Surface  measured FWHM delta CWL Notes
Barr Associates

Sol'Ex spectro f-115 10 micron × 4.5 mm 2.6 A

-0.7 A

2-cavity filter

Alluxa
Sol'Ex spectro f-115 10 micron × 4.5 mm 3.7 A +2.2 A 3-cavity filter



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