New eShel spectrograph

[2SPOT]

We have received our new eShel spectrograph from Shelyak Instruments for our setup in Chile.

Before installing this new spectrograph in Chile, we are going to do some tests in France.

First test today, with the daylight.
The spectrograph is equip with a 135mm Canon lens and an ASI 2600 mm pro camera (CMOS technology)


Here's the Th/ar lamp spectrum. The Shelyak calibration module cut the IR part of the spectrum to prevent any Argon pollution (from very intense lines in the near IR) after 8000Å



We can process orders up to #61 (with the Sun)

And here's our RMS wavelength calibration (we can improve it for some orders, this is only the first process, we can adjust some parameters in the futur to have better RMS, less than 0,01Å)

Ordre #30 : RMS = .0110 - Nb. raies = 9
Ordre #31 : RMS = .0103 - Nb. raies = 12
Ordre #32 : RMS = .0074 - Nb. raies = 13
Ordre #33 : RMS = .0057 - Nb. raies = 13
Ordre #34 : RMS = .0112 - Nb. raies = 17
Ordre #35 : RMS = .0070 - Nb. raies = 14
Ordre #36 : RMS = .0058 - Nb. raies = 13
Ordre #37 : RMS = .0036 - Nb. raies = 13
Ordre #38 : RMS = .0158 - Nb. raies = 16
Ordre #39 : RMS = .0069 - Nb. raies = 12
Ordre #40 : RMS = .0095 - Nb. raies = 16
Ordre #41 : RMS = .0898 - Nb. raies = 17
Ordre #42 : RMS = .0231 - Nb. raies = 14
Ordre #43 : RMS = .0050 - Nb. raies = 10
Ordre #44 : RMS = .0119 - Nb. raies = 17
Ordre #45 : RMS = .0092 - Nb. raies = 12
Ordre #46 : RMS = .0153 - Nb. raies = 18
Ordre #47 : RMS = .0077 - Nb. raies = 13
Ordre #48 : RMS = .0079 - Nb. raies = 15
Ordre #49 : RMS = .0014 - Nb. raies = 9
Ordre #50 : RMS = .0034 - Nb. raies = 12
Ordre #51 : RMS = .0031 - Nb. raies = 17
Ordre #52 : RMS = .0035 - Nb. raies = 16
Ordre #53 : RMS = .0022 - Nb. raies = 13
Ordre #54 : RMS = .0060 - Nb. raies = 14
Ordre #55 : RMS = .0059 - Nb. raies = 12
Ordre #56 : RMS = .0058 - Nb. raies = 14
Ordre #57 : RMS = .0096 - Nb. raies = 15
Ordre #58 : RMS = .0097 - Nb. raies = 13
Ordre #59 : RMS = .0105 - Nb. raies = 14
Ordre #60 : RMS = .1085 - Nb. raies = 12
Ordre #61 : RMS = .1053 - Nb. raies = 7

And the resolution

Order #30 : R = 10499.0
Order #31 : R = 9868.4
Order #32 : R = 10626.8
Order #33 : R = 10830.4
Order #34 : R = 10655.3
Order #35 : R = 11534.3
Order #36 : R = 11863.7
Order #37 : R = 12176.8
Order #38 : R = 10752.4
Order #39 : R = 11754.3
Order #40 : R = 11607.5
Order #41 : R = 10664.4
Order #42 : R = 11313.1
Order #43 : R = 11591.3
Order #44 : R = 11191.1
Order #45 : R = 11494.7
Order #46 : R = 11815.0
Order #47 : R = 11828.2
Order #48 : R = 11722.2
Order #49 : R = 12453.0
Order #50 : R = 11749.6
Order #51 : R = 12346.3
Order #52 : R = 12071.6
Order #53 : R = 12038.4
Order #54 : R = 11017.6
Order #55 : R = 11914.1
Order #56 : R = 11123.9
Order #57 : R = 10361.5
Order #58 : R = 11084.6
Order #59 : R = 11458.5
Order #60 : R = 10521.1
Order #61 : R = 12028.3

And some graphs of the Sun spectrum process with ISIS 6.1.1. and the CMED algorythm (to remove CMOS telegraph noise).
No instrumental response use with this first test, only tungsten lamp from the calibration module.

H Alpha


D1 and D2 lines


H and K lines


Next step : on the sky to test the limit magnitude and SNR with our setup. (a RC12) and spectrograph accuracy vs temperature

[Michel Verlinden]

Bonjour,

Un eshel au Chili ! 2Spot l'a fait !

Merci pour ces tests combinés (eshel amélioré, canon 135 F2 L , ASI 2600 MM).
Olivier, comment les raies de l'IR sont-elles coupées ? Utilisez-vous un filtre spécial ?
Les raies de calibration sont elliptiques sur l'image présentée. Je vois que cela ne gêne pas la précision de calibration.
Quelle est cependant la cause de cette forme allongée ?

Amicalement,
Michel Verlinden

[Olivier GARDE]

Michel,

Dans le boitier de calibration de l'eShel Shelyak, il y a un filtre qui coupe les longueurs d'ondes >8000Å de mémoire afin que les raies de la lampe Th/Ar (surtout l'Argon) ne viennent pas polluer les ordres plus haut que l'ordre 30, sinon cela rajoute des raies phantomes qui nuisent à la calibration spectrale. (les raies de l'Argon sont vraiment très intenses et contamines les autres ordres comportant principalement du Thorium, plus faible en intensité que les raies de l'Argon). Ce filtrage n'intervient que sur la source de la lampe de calibration, pas sur le spectre de la cible.

Oui l'image montre des raies en forme d'ovale mais c'est corrigé dans le process ISIS en indiquant ordre par ordre une valeur d'un angle (un peut comme un angle de slant en fait) qui permet d'avoir des raies bien circulaires.

On doit encore optimiser les réglages et faire des essais sur des cibles stellaire et faire pas mal de test avant de l'envoyer au Chili....

[2SPOT]

We continue our tests on the spectro eShel which turns out to be very stable and we agree with this article that we found and which compares eShel with Baches :
https://iopscience.iop.org/article/10.1 ... 115001/pdf

The value of 0,25km/s is what we have found on our spectrograph. We think that we can have better result with a thermal regulation enclosure. (a shift on a line close to H Alpha around 0,005 Å).
To maintain this precision it is also necessary to have a good spectral calibration with a RMS close to 0,0005Å.

[2SPOT]

We tried our eShel spectro on the sky. Here is the spectrum of Vega always realized with the ASI 2600 MM pro and a lens of 135mm.


The spectrum have an average of R=11000 from all orders (from #30 to #58). Some orders in the red have a resolution below 10.000.

and a detail on the blue edge of the spectrum


Our processing with ISIS could be improved and we think that we can go up to order 60 but remain at order 30 because of the filter of the calibration lamp (to prevent any pollution of the Argon on the spectrum up to 8000 Å).

[2SPOT]

The tests continue with our eShel spectrograph before it's sent to Chile.
Here we have take a P Cyg spectrum always with the objective lens of 135mm and the ASI 2600 MM pro camera (and of course the CMED process of ISIS to get rid of the telegraph noise)



the wavelength limit is around 3810 Å in blue and 7600 Å in red (so as not to be polluted by the Argon calibration spectrum)

Another target gam Cyg with the H and K lines.



On the extreme orders in the blue (#59, #58, #57, #56), the resolution is around 10.000 to 10.500. (we have focus the spectrographe on order #47 with R=12.700)

The thermal stability of the eShel is very good (less than 0,5 km/s per degree Celsius).