The filter was measured using three different approaches:
- interferometry using an Ha lamp.
- Sol'Ex spectrometer in collimated beam (f/115 beam),
- Sol'Ex spectrometer with f/27.5 telecentric beam,
- interferometry using an Ha lamp.
- Sol'Ex spectrometer in collimated beam (f/115 beam),
- Sol'Ex spectrometer with f/27.5 telecentric beam,
| Filter | Test method | f-ratio | Surface measured | FSR | FWHM | delta CWL | |
| DayStar PE 0.6A | Ha lamp | collimated | Full aperture |
N/A | 1.0 A |
tuned on Ha |
|
| Sol'Ex spectro | f-115 .. f-27.5 telecentric |
10 micron x 4.5 mm | 25.9 A ... 26.0 A |
1.0 A .. 1.1 A Peak transmission = 7% |
thermo-regulated etalon, tuned on Ha at f-27.5 .... thermo-regulated etalon, tuned on Ha at f-27.5 |
... ... BW at 10% transmission = 2.7 A |
Sol'Ex spectrometer: measurement in a f/27.5 telecentric beam
Optical setup: Sun => Hat 8 telescope with f/27.5 telecentric beam => Filter => Sol'Ex spectrograph
10 microns slit, 80 mm collimating lens, 125 mm imaging lens, ASI290 camera, 12-bit acquisition.
Measured dispersion = 0.075 A/pixel
11 June 2021
Three succesive images :
- solar spectrum,
- solar spectrum transmitted by the DayStar PE 0.6 A at 6562.9 A setting, this spectrum is registered to the solar spectrum. The leakage of phostosheric light on both side of theHa line is obvious.
- same as before but with different vizualisation thresholds.
- solar spectrum,
- solar spectrum transmitted by the DayStar PE 0.6 A at 6562.9 A setting, this spectrum is registered to the solar spectrum. The leakage of phostosheric light on both side of theHa line is obvious.
- same as before but with different vizualisation thresholds.
The FSR is equal to 26.0 A.
The transmission profile of the etalon is given by the ratio "transmitted solar spectrum / solar spectrum". The profile was measured with two different settings of wavelength. The results are the same.
The direct measurement on the graph at 50 % and 10 % peak transmission give:
- FWHM = 1.05 A
- BW at 10% peak T = 2.7 A
To improve accuracy of the measurement, the transmission profile was also fitted by a voigt curve (which gives a better fitting than a Lorenztian):
- FWHM = 1.05 A
- FWHM = 1.05 A
- BW at 10% peak T = 2.7 A
To improve accuracy of the measurement, the transmission profile was also fitted by a voigt curve (which gives a better fitting than a Lorenztian):
- FWHM = 1.05 A
NB : same results obtained on June 10, 2022 with an improved
configuration of Sol'Ex (125 mm f.l. collimating and imaging lenses,
ASI290)
Estimated of peak transmission = 7%
(June 10, 2022)
(June 10, 2022)
Sol'Ex spectrometer: measurement in a collimated beam (f/115)
Optical setup: Sun => DayStar filter => Sol'Ex => ASI290
Sol'Ex spectrograph : 10 microns slit, 80 mm collimating lens, 125 mm imaging lens, ASI290 camera, 12-bit acquisition.
Measured dispersion = 0.0753 A/pixel
13 June 2021
- FSR = 25.9 A.
The measurements at 50 % and 10 % peak transmission give :
- FWHM = 1.0 A
- BW at 10% peak T = 3.4 A (wing measurements polluted by oscillations due to Ha line)
The fitting of the transmission profile by a Voigt function gives :
- FWHM = 1.0 A
The measurements at 50 % and 10 % peak transmission give :
- FWHM = 1.0 A
- BW at 10% peak T = 3.4 A (wing measurements polluted by oscillations due to Ha line)
The fitting of the transmission profile by a Voigt function gives :
- FWHM = 1.0 A
Measurement of the etalon with a Ha lamp
Nikon Z6 with 50 mm S f/1.8 lens at f/2 - center of the etalon - 30 s exposure - 100 ISO - 2 March 2021
Etalon gap index :
The main assumption to be made in the measurement with a Ha lamp is about the index of the etalon gap. This value is directly related to the FSR. Given that the FSR measured by spectrometry is equal to 26.0 A at operating temperature, we can trace back the index to about 1.57.
FWHM measurements :
On this basis, the average value of FWHM measured over the full diameter of the etalon is 1.01 A, and 1.02 A over a 4.7 mm diameter (at normal incidence).
The main assumption to be made in the measurement with a Ha lamp is about the index of the etalon gap. This value is directly related to the FSR. Given that the FSR measured by spectrometry is equal to 26.0 A at operating temperature, we can trace back the index to about 1.57.
FWHM measurements :
On this basis, the average value of FWHM measured over the full diameter of the etalon is 1.01 A, and 1.02 A over a 4.7 mm diameter (at normal incidence).