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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:

PHD2_slit_Neowise.png.b88c7b14bc9cd8a2c954cf49bb2e8511.png

Spectrum with stretched histogram, faint LP of my city is present in the background, 5x60s stack:

218378053_SpectrumLP.thumb.PNG.a66c4b018dc09134f2d65ab96d046b52.PNG

I hope that I correctly substracted LP from the comet spectrum.

The result obtained in the BASS software:

Neowise_spectrum.thumb.PNG.c5185203b639cb531749330a6ca2f7cf.PNG

We have carbon C2 bands, CN and strong emission of sodium doublet. Some lines are unidentified yet.

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Very nice work. Regards Andrew 

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Well done!

Good result. Interesting that the Sodium peak appears to be diminishing, and the Swan bands increasing..

 

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Posted (edited)

Last night I recorded again the comet's head spectrum. NEOWISE has weakened significantly. There was a big change in 5 days. No sodium NaD emission. This comet is more green due to emission in the C2 Swan bands.

Comparison below:

Neowise_spectra.thumb.png.e2b4051d33fdb5bd972b501fc973b164.png

Plot.thumb.PNG.73395329b53143f93918fb0e7fd9e6be.PNG

 

Edited by Bajastro
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Another great result! Well done.

You're certainly putting the LowSpec through its paces.

 

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Posted (edited)
On 20/07/2020 at 13:09, Bajastro said:

No sodium NaD emission.

There is still some around showing at high resolution in this raw image from last night under poor conditions (LHIRES 1200 l/mm R~11500)

neowise_20200720.jpg.8eddb4ab3474b5470e08b93ab94ef52c.jpg

but significantly less than 10 days ago when the comet was closer to the sun

F3_raw_LHIRES1200_20200710.png.140643cd8a7b2efc58d3c3a2c23f346c.png

 

Note how the displacement between the comet and sky emission lines due to the Doppler effect has reduced as the comet is moving slower in our direction  relative to us now

 

Cheers

Robin

Edited by robin_astro
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