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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.
I finished observations of the Mizar A spectroscopic binary. Calibration for the Hα line made on water lines contained in the Earth's atmosphere. I used LowSpec spectrograph with 1800 grooves/mm reflective holographic grating, APM APO 107/700, QHY163M camera and HEQ5 mount with guiding. It turned out that the Earth's movement practically compensated for the radial velocity of the Mizar A system. Based on the analysis, I received the result: vr = -8.8 km/s in fact the system is approaching at a radial velocity of -6.3 km/s. I also determined the phase plot of radial velocities based on my measurements for the Na (together for both lines) and separately for Hα line: Error is based on half my spectral resolution (0.2 Å/pix corresponds to rv = 10 km/s). Each measurement corresponds to the stack a few images. The most important purpose of observing this binary system was to record the historical Ca II line (often called as CaK, 3933.66 Å). The distances in the violet part of the spectrum are almost 2x smaller than the corresponding shifts for the Hα line. This line initiated the discovery of spectroscopically binary systems, and Mizar A was the first discovered system of this type. These were the spectroscopic observations in the 19th century: Source: https://www.leosondra.cz/en/mizar/#b20 I've made several observations of this line in the last two weeks: Animation showing the changes in the CaK line based on my observations: Not only the Ca II is split, but the surrounding lines also, shown below in a wider environment: Balmer hydrogen lines are becoming more dense as Balmer's gap approaches (3646 Å). Observation result of the Hα line: And animation showing the changes in this line: The Na I doublet was much more difficult to observe, because stars with A spectral type contain very faint lines of this metal: Animation showing the changes in the sodium doublet: We received the sodium quartet