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Old 25-12-2021, 06:28 PM
Rob_K
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Spectra of comet C/2021 A1 (Leonard)

This comet has proved interesting since it entered southern skies in bright twilight on 16 December. I've managed to image it nearly every night since and I've obtained a spectrum twice (well, three times but the first was so noisy it was virtually unusable! ). It has had two major outbursts in the last week and last night it was a very easy naked-eye get in the western sky, like a fuzzy star and mag 3.1 by my estimate.

Last night's spectrum is attached as well as a comparison between the two spectra obtained - no real change visible. They show diatomic carbon emissions climbing over a continuum from sunlight reflection off the dust. Also a night-to-night montage of the comet.

Anyway, if you want to see it, get in quick because it may not survive much longer!

Cheers -
Attached Thumbnails
Click for full-size image (A1 spectrum, 24 Dec 2021 text sm.jpg)
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Click for full-size image (A1 spectra, 20 & 24 Dec 2021 text sm.jpg)
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Click for full-size image (A1 18-24 Dec 2021 montage sm.jpg)
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Old 25-12-2021, 07:56 PM
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erick (Eric)
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Been clouded out every evening for over a week Forecast for early evenings unchanged for the rest of this week
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Old 26-12-2021, 07:40 AM
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Merlin66 (Ken)
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Rob,
Well caught!
What optics did you use for the images of the comet?
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Old 26-12-2021, 07:34 PM
Rob_K
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Rob,
Well caught!
What optics did you use for the images of the comet?
Thanks Ken. I was just using a Canon 800D DSLR and a 200mm lens. I've been driving up to a mountaintop location via unsealed forestry tracks so I'm travelling light!

Hope you had a good Christmas!

Cheers -
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Old 31-12-2021, 10:26 AM
John W (John Wilkinson)
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Rob, Nice set of images and spectra - How does the spectra compare to those of other comets? Interpretation? Thanks. John W.
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Old 31-12-2021, 07:52 PM
Rob_K
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Rob, Nice set of images and spectra - How does the spectra compare to those of other comets? Interpretation? Thanks. John W.
Thanks John! The spectra I've taken show it as a comet with good contributions from both gas (emissions) and dust (reflections). A very gassy comet would show a flat spectrum with high emissions while a very dusty comet would show a broad high continuum with little in the way of peaks from gas emission. The C2 (diatomic carbon) emissions are typical - however sometimes other emissions will show (eg sodium if a comet goes close enough to the Sun) so it's worth monitoring for changes.

Cheers -
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Old 31-12-2021, 08:36 PM
AdamJL
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Brilliant, love the science here. And great images to boot.
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Old 01-02-2022, 08:36 AM
hamishbarker
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Great work Rob! Where are you observing from? (I'm quite familiar with the mountains around Bright from half a lifetime of paragliding).

I managed to get a spectrum of the same comet just before the new year, so will post it when I'm home.

Rob, please let us know if you would like any assistance with the process of taking reference star spectra so that your camera/lens spectral response can be calibrated.

Cheers,
Hamish
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Old 02-02-2022, 08:11 PM
Rob_K
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Originally Posted by hamishbarker View Post
Great work Rob! Where are you observing from? (I'm quite familiar with the mountains around Bright from half a lifetime of paragliding).

I managed to get a spectrum of the same comet just before the new year, so will post it when I'm home.

Rob, please let us know if you would like any assistance with the process of taking reference star spectra so that your camera/lens spectral response can be calibrated.

Cheers,
Hamish
Thanks Hamish! I observe from home on the outskirts of Bright usually but these were taken from Clearspot Lookout, my go-to when I need flatter horizons. The "calibration approximate" refers to my use of a DSLR & lens, where there are lens aberrations and no really effective way of ensuring that the target is always in exactly the same position and that the spectrum is always cast at exactly the same angle. I have lots of sharp clear star spectra for calibration - novae for example are very useful.

Look forward to seeing your spectrum!

Cheers -
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Old 03-02-2022, 01:52 PM
hamishbarker
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Here's a spectrum of comet Leonard which I took in late December.

The line identifications are just guesses.
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Old 04-02-2022, 01:31 AM
Rob_K
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Beautiful job Hamish!

Cheers -
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