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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.
Today after the midnight I recorded the spectrum of C/2020 F3 (Neowise). I couldn't change new diffraction grating (300 l/mm) before the midnight in my Low Spec 2 spectrograph. I have printed second unmodified mounting for grating and I had to use it, because dispersion angles are different than the 1800 l/mm diffraction grating. It was also necessary to assemble and run the setup. Not all lines were identified, the spectrum is different than spectra published on the internet. The violet range is worse due to the poor correction of chromatic aberration in achromatic lenses in my Low Spec and my APO, so lines are weaker. Intensity hasn't been corrected. I think that this comet was too low above the horizon to do it well. This is also the first light with a diffraction grating 300 l/mm used in the Low Spec 2.
Slit position, PHD2 screen:
Spectrum with stretched histogram, faint LP of my city is present in the background, 5x60s stack:
I hope that I correctly substracted LP from the comet spectrum.
The result obtained in the BASS software:
We have carbon C2 bands, CN and strong emission of sodium doublet. Some lines are unidentified yet.
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.
I managed to get some time to process another of my images exposed in January/February 2020.
This was the last image when my USB port on my Astro40D failed. This happened while imaging this scene but it happened toward the end of the imaging plan so I got almost the subs that I wanted. The total exposure time was 16 hours and 16 minutes in ISO1600 for all of the subs, RGB, (OSC through the UV/IR Cut filter), HAlpha and OIII.
Imaged through my 8" SCT at f6.3, 1280mm FL.