etalonnage raies H & K

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etienne bertrand
Posts: 1040
Joined: Mon Aug 31, 2015 11:26 am

etalonnage raies H & K

Post by etienne bertrand »

Bonjour,

J'ai essayé de chercher sur le forum, mais je n'ai pas trouvé comment on calibre les spectres sur les raies H & K ?
Pour le soleil, j'ai pu le faire avec les longueurs d'ondes qu'elles ont mais pour les étoiles comment fait on ?
Merci.
etienne bertrand
Posts: 1040
Joined: Mon Aug 31, 2015 11:26 am

Re: etalonnage raies H & K

Post by etienne bertrand »

Raies H & K du CaII sur le Soleil, calibrées avec les 2 longueurs d'ondes H et K du CaII via ISIS.
Caméra utilisée ASI78MM, à noter que dans ces longueurs d'ondes il n'y a pas de franges interférences. Sinon elle sont a peu près présentes partout ( H2O, Ha, doublet NaI, triplet de MgI, ...). La résolution est calculée sur des raies d'absorptions, c'est pas très précis mais ça donne une bonne idée.
La raie d'absorption profonde à 4005A, c'est une raie du fer non ?
Image

Avec la réponse instrumentale
Image
Last edited by etienne bertrand on Wed Feb 28, 2018 4:57 pm, edited 3 times in total.
etienne bertrand
Posts: 1040
Joined: Mon Aug 31, 2015 11:26 am

Re: etalonnage raies H & K

Post by etienne bertrand »

Au fait, pourquoi ces 2 raies H et K qui sont du CaII (ionisé) ne sont pas en émission, mais en absorption ? (je penses par exemple au raies [OIII] qui sont en émission le plus souvent..)
etienne bertrand
Posts: 1040
Joined: Mon Aug 31, 2015 11:26 am

Re: etalonnage raies H & K

Post by etienne bertrand »

Peu mieux faire, la caméra de guidage (Dfk21) n'était pas idéale... la fente de 15µm peut être un poil serrée, et les petits pixels de l'ASI178MM ne facilitent pas les choses pour accumuler le flux. A refaire avec une meilleure caméra de guidage et la fente de 35µm. Certainement que des pixels de 3/4 µm offrent le meilleur compromis si on veut travailler jusqu'à des magnitudes 6 et +

Sirius :
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Capella :
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Aldébaran :
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Betelgeuse :
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Gam Cas :
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Zet Tau :
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Setup :
Setup :Image
Last edited by etienne bertrand on Wed Feb 28, 2018 4:57 pm, edited 1 time in total.
Peter Somogyi
Posts: 420
Joined: Sun Jul 13, 2014 8:56 am

Re: etalonnage raies H & K

Post by Peter Somogyi »

Dear Etienne,

"J'ai essayé de chercher sur le forum, mais je n'ai pas trouvé comment on calibre les spectres sur les raies H & K ?"

Assume your question is about how to calibrate this region. This is the CALIB file I am using (for ATIK 428 EXm), produced by Ar/Ne internal lamp (clothed by packaging plastic):

2
0.16541492537313432835820895522388
3868.528
3925.719
3932.547
3979.356
3994.792

I take at least 2 x 15 seconds (before & after each exposure).
The calibration gets mistaking (and defocused) towards the CCD edges, possibly because the internal Ar/Ne lamp following a bit different light path when unfocused.

For the flat, unfortunately the internal flat lamp is a no-go here (produces reflections and ambient lights in the UV). You need to prepare a custom method.
I personally use a "Black Light Bulb" tube, producing a few known emissions that I cancel manually. (For the lower 3720 - 3865A, I have no emission so using it normally.)
Today I realize not much DIY skills needed for this, such a bulb can be ordered in a regular E27 (or smaller) socket.
I have seen others referred to a high temperature halogen, however I have no practice with that, and suspect about similar problem as the internal lamp.
Only trick is the diffuser, semi-transmitting plastic should work.
Other method instead flat, is to shoot a well chosen ref.star as an IR calibration, but I have no practice for in that at this resolution.

To identify features, I use VSpec while reading articles about the target (adsabs, arxiv). If you could extract such a list per target, I'd certainly look.
In general, when the CaII 3933 exists, the other K line is contaminated by Balmer (that usually always present). Hence my recommendation was to always put the focus somewhere between the CaII 3933A and H8. The K and H7 can't be easily analysed due to the overlap (works only as a "checksum"), always prefer 3933 when need to chose.

Cheers,
Peter
etienne bertrand
Posts: 1040
Joined: Mon Aug 31, 2015 11:26 am

Re: etalonnage raies H & K

Post by etienne bertrand »

Hello Peter,

Thanks for your response. You have goods results spectra !

WIth the ASI178MM caméra in the environnement of H & K lines i don't see rays of Argon/Neon LhiresIII lampe. Is it's normal ?
I use LhiresIII with greating 2400tt/mm and ASI178 = 3096x2080 pixels of 2.4µm (7430 x 4992 µm).
For calibrate my spectras i use the H&K and Fe rays, so the spectras are corrected of heliocentric velocity...
For an other try i must change the dfk21 caméra, it's not very good for seeing and guiding. With an other i should make better results (SNR, star in slit...).
Can you post a capture of the Argn/néon rays in this wavelengts ? You use this greating ?
Peter Somogyi
Posts: 420
Joined: Sun Jul 13, 2014 8:56 am

Re: etalonnage raies H & K

Post by Peter Somogyi »

Hello Etienne,

Here is one of my calibration frame (ATIK 428 EXm, -15C, bin2x2, 35 micron photometric slit, 15 sec exposure):
127_vvcep-cal.jpg
127_vvcep-cal.jpg (39.97 KiB) Viewed 4176 times
I take 2 of this, before/after an exposure (typical real targets are multiple minutes).
Forgot to mention, with the original (non-photometric) slit, I have a poor reflection destroying my uv-flats in the middle. Hence I always prefer the photometric slit (fortune to have here), that somehow better.

Your possible problem is, that you have the Neon bulb (yellowish light), whilst the Ar/Ne bulb is purplish. Also the material of diffuser may be important, paper might be cutting here (plastics usually work better in the UV).

Cheers,
Peter
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