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On 3-rd of September, just before sunset, I set up my equipment, aimed the telescope towards the zenith, set the spectrograph on the double sodium line and every now and then ran a series of photos, adjusting the exposure time (30-120 s) and gain. At the end it was so dark that the gain had to be increased almost to "what the factory gave". I was not sure if we would be able to register anything at the resolution of 1800 l/mm holographic diffraction grating, slit with 40 μm wide. I also tracked the height (the depth of the sun below the horizon). I read in some publications that when the Sun is about 8° below the horizon, mesospheric sodium layer is in emission near the zenith above the observation site. Two disappearing absorption lines and emission lines appearing in their place were recorded: And an animation with the given position of the Sun relative to the horizon: The capabilities of the printed in 3D technology my Low Spec spectrograph are amazing.
Few days ago I decided to observe the spectra around Na lines for Jupiter and Saturn. I had a little time and some problems with Bluetooth communication. It took me about 30 min. About 3 am the sky was getting brighter. I set 20 μm slit of my Low Spec spectrograph along the equator: These images were taken few years ago. 1, 2, 3 - positions of spectral profiles The goal was to record the impact of planetary rotation on the shape of spectral lines. Interestingly, the spectra contain not only the inclined lines created due to the Doppler effect. There are also visible vertical absorption lines of the Earth's atmosphere, there are quite a few of them. Below two stacks of Na doublet area, resize 200%: Spectral profiles for Jupiter: Spectraf profiles for Saturn Rings: The result of calculations of the rotational velocity at the equator and comparison with data in the public literature: Result of calcutations Jupiter Saturn Rotational velocity 13.2 ± 1.3 km/s 10.5 ± 1.3 km/s Equatorial diameter 149890 km 128744 km Public literature Jupiter Saturn Rotational velocity 12.6 km/s 9.87 km/s Equatorial diameter 142984 km 120536 km The velocity of Saturn's rings is variable, the rings closest to the planet have the highest velocity, the furthest rings are the slowest. The calculated average velocity based on the recorded spectrum is 15.8 km/s. As an example, the velocity of the crumbs moving on the outside of the Cassini Break (ring A) is 17.5 km/s. Pretty close. I took half a pixel as a measurement error.