Quark combo

(August 2023)

This Quark combo was bought in 2023.

General information:
- temperature of the oven increases when the tuning knob is rotated clockwise,
- min temperature (7h position) = 29°C, max temperature (17h position) = 40.1 °C,
- CWL swing from min to max temperature = 1.2 A (=(40-29)/9 ),
- the CWL of this filter is on Ha when knob is at 9 h position (at 25°C ambient temperature).

Visual and imaging assessement:
The contrast of images is very low. Double-limb effect is prominent. 

Testing approach and main results:

The filter was measured using the following approach:
- Ha lamp (diffuse light),
- Sol'Ex spectrometer in a collimated beam (Sun >> Quark combo >> Solex >> ASI290)

Filter Test method f-ratio Surface  measured FSR FWHM Bandwith at 10% peak transmission
Quark combo Ha lamp NR full aperture NR 2.0 to 2.1 A NR

Sol'Ex spectro
(fc =fi = 125 mm, ASI290, 0.0757 A/px dispersion)
f/115 10 micron x 4.5 mm 20.1 A
2.0 to 2.1 A

Test with the Ha lamp

Quark combo - Nikon Z6 - Nikkor 50 mm f/1.8 S at f/2 - 800 ISO - 20 s exposure - 12 bit acquisition - red channel

Measured FWHM is between 2.0 to 2.1 A

Sol'Ex spectrometer: measurement in a f/115 telecentric beam

Optical setup: Sun =>
Quark with its BF => Sol'Ex spectrograph => ASI462

10 microns slit, 125 mm collimating lens, 125 mm imaging lens, ASI462 camera, 12-bit acquisition.
Measured dispersion = 0.0757 A/pixel
Conditions : blue sky

Four succesive images :
- Solar spectrum (= no filter).
- Solar spectrum transmitted by the Quark combo at ambiant temperature (about 23°C). This spectrum is registered to the solar spectrum.
- Same as above, but different vizualisation thresholds.

The FSR is between 20.1 and 20.2 A

The transmission profile of the etalon is given by the ratio "transmitted solar spectrum/solar spectrum". 


The direct measurement on the graph at 50 %  peak transmission give an FWHM of 2.2 A, which is consitent with the measurement with the Ha lamp.

NB : the intensity of the two transmission peaks at -20A and +20 A is not equivalent, which is a possible indication of the BF transmission curve not centered on Ha.

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