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Re: comète 46p/wirtanen Alpy600 T400

PostPosted: Tue Dec 18, 2018 10:15 am
by James Foster
Here are my visual spectral results for Comet Wirtanen's closest approach to Earth (16Dec18) with my Alpy600. Unfortunately I had to do this from my heavily light
polluted backyard (less than 10 miles away from downtown Los Angeles- 12 million people in the County alone!). Here is the Alpy spectra I got after using the Miles
star HD19373 for my IR spectra:
Image
Here is the 2D of the spectra after processing it in IS:
Image
[Note: All identified spectral C and NH2 species speculative!]

Finally, I tried to implement a spectra curve of the object with the light of the sun removed, as Robin demonstrated. I used the nearby solar analog star HD10307,
with a spectra type of G1V. Here is the resulting spectra graph (blue for the divided spectra):
Image

I'm sure this just represents the "dusty" area of the central pseudo-nucleus....I'll need to practice more IS to get only the gas emission component of the spectra.
After taking these visual spectra, I quickly swapped the Alpy600 for my LISA in Infrared mode and got some spectra in the 6200-9600A region, which I still need
to process.

James

Re: comète 46p/wirtanen Alpy600 T400

PostPosted: Tue Dec 18, 2018 12:19 pm
by Robin Leadbeater
Hi James,

Good to see our measurements of the reflectance spectrum agree. Yes after discussions with the BAA Comet Section director on the BAA forum and some measurements on my spectrum image at different distances from the centre showing a similar result, it does seem we are probably seeing just the dust and not the nucleus.
https://britastro.org/comment/5855#comment-5855

Cheers
Robin

Re: comète 46p/wirtanen Alpy600 T400

PostPosted: Tue Dec 18, 2018 2:16 pm
by Erik Bryssinck
Hello all,

Here my result of the 46P/WIRTANEN spectrum taken on 12 dec at about 20:29 UT. I live in a high light-polluted area and it is always difficult to correct the background and substract the light-pollution. I took 10 x 600 sec images of 46P with the ALPY600 and after that about 5 x 600 sec of trhe background on almost the same altitude as the images of 46P taken before. I see in all the 46P spectra images
a change in the background due the climb of the comet during the observation. Unfortunately i couldn't take a sunlike star because clouds where coming in. After the dark and flat and background substraction. as correction of the sun spectrum i took a spectrum from the catalog of a G2V star. I got the result below.

Re: comète 46p/wirtanen Alpy600 T400

PostPosted: Thu Dec 20, 2018 1:08 am
by James Foster
Here is my LISA IR Spectra of Comet Wirtanen taken right after my Alpy600 data on 16Dec18:
Image
NOTE: All non-telluric lines shown are speculative
Here is the 2D .fits file image generated by IS after processing:
Image

I used this and the Alpy600 data with the 2 solar type (HD10307-G1V & HD28099-G2V) stars shots to produce this graph of the comet without the solar continuum contribution:
Image
This "Divided" curve probably represents the "dusty" pseudo-nucleus of the comet. I'll process the Alpy and LISA IR 2D images to eliminate the central
"dust" component to get the emission "gas" component as Erik's fine work demonstrates.

James

Re: comète 46p/wirtanen Alpy600 T400

PostPosted: Thu Dec 20, 2018 3:33 pm
by Christian Buil
An intermediate resolution (R=2600) of 46P during test session of UVEX3 spectrograph (see http://www.spectro-aras.com/forum/viewtopic.php?f=8&t=2193&p=11981#p11981). A 2D image (18 December, the sky background is illuminated by the Moon, RC10 telescope , UVEX3 + 1200 l/mm grating, Atik414EX camera) :

Image

The spectral profile (instrumental spectral response not removed) :

Image

Spectral response corrected (tentative, not a so easy task beccause sky background) :

Image

Christian Buil

Re: comète 46p/wirtanen Alpy600 T400

PostPosted: Thu Dec 20, 2018 10:16 pm
by etienne bertrand
Superbe Christian !! Déjà que le spectre avec l'eshel était une belle prouesse, avec l'Uvex3 c'est un bel exploit !
Serait il possible d'avoir le spectre de 46p en .fit en pièce jointe pour pouvoir y superposer un spectre Alpy avec R=600 ?
Image

Re: comète 46p/wirtanen Alpy600 T400

PostPosted: Fri Dec 21, 2018 10:02 am
by Gerard Arlic
etienne bertrand wrote:Serait il possible d'avoir le spectre de 46p en .fit en pièce jointe pour pouvoir y superposer un spectre Alpy avec R=600 ?
Image

+1 :)

Re: comète 46p/wirtanen Alpy600 T400

PostPosted: Wed Jan 02, 2019 7:56 pm
by Hubert Boussier
Bonsoir et bonne année 2019,

Les conditions étaient bonnes dans le sud le 29 décembre, avant que 2019 nous amène un Mistral à décorner les bœufs et faire monter le seelng à 20 arcs, j'ai pu faire ce spectre de 46P.
C8 réduit à F/d 6,2 10x600s LISA fente 23 micron Atik 414 EX. Pollution lumineuse bien présente QSM 19,5. La résolution est d'environ 950.

Image

La résolution atteinte permet de séparer les raies principales de NH2 dans la bande (0,7,0).

http://adsabs.harvard.edu/full/1996AJ....112.1197B


Image


Bon ciel

Re: comète 46p/wirtanen Alpy600 T400

PostPosted: Wed Jan 02, 2019 8:31 pm
by etienne bertrand
Salut Hubert,
Ca c'est du spectre de comète !! bravo c'est vraiment bien résolu.

Re: comète 46p/wirtanen Alpy600 T400

PostPosted: Sat Jan 05, 2019 10:19 am
by Daniel Dejean
Enfin une soirée claire après plusieurs semaines très nuageuses...
C’est peut être un peu tard pour observer 46P/Wirtanen. Sur cette image brute obtenue dans la nuit du 03janv19, la trace du spectre de la comète a bien du mal à s’élever au dessus de la pollution du fond du ciel .

Image

Mais Isis fait des miracles et, avec un peu d'attention ;) , il est possible de distinguer quelques raies significatives malgré un très mauvais rapport signal sur bruit. Sur le graphique ci-dessous, le spectre de 46P/Wirtanen est comparé à celui d’une étoile voisine de type G5 : hd59033 obtenu dans la même soirée. Je n'ai pas trouvé de G2V suffisamment proche, mais cette approximation ne paraît pas gênant pour cet exercice très rudimentaire de comparaison visuelle.

Image

Bonne nouvelle année et bon ciel à tous !