Observatoire de la belle étoile: janvier 2016

Following a question I received, here is an image of the fiber injection unit mounted on a C11 telescope with a 0.64x focal reducer and a Meade flip-flop mirror (used when I want to do some visual with the telescope & some friends!):

Distance from the back of the focal reducer to the front plate of the fiber injection unit is around 80mm. Adding 41mm for the distance from that front plate to the slit/mirror, the distance from the focal reducer to the slit is around 120mm (85mm is the nominal distance for that focal reducer). I'm then working around F/5...

Let's check this by using a long (20s) exposure of the field around CW Cep, with an Atik Titan camera (pixel size: 7.4µm):

Here is the field of view in Guide 9 starchart and the measured distance between the two marked stars: 365"

dX & dY for those two stars on the guiding image are dX=408 pixels & dY=388 pixels, giving a distance on the sensor of 4.17mm.

For a 280mm diameter telescope (C11), taking into account that the guiding port of the eShel fiber injection unit has an internal 1.5x barlow, this gives a true telescope focal at F=1570mm, so a F/ ratio of F/5.6.

Another way is to use Astrometry.Net: http://nova.astrometry.net/

I uploaded the image and obtained this result:

Then remember the formula:

telescope focal (mm) = 206 x pixel size (µm) / pixel scale("/pixel)

So in this case F = 206 * 7.4 / 0.664 = 2296mm, to divide by 1.5x to take into account the barlow inside the eShel fiber injection guiding port: F=1530mm, so F/5.5.

While I'm observing some Be stars(cf previous log on Be stars and ARASBeAm), I have taken some screen shots to illustrate how the eShel data reduction works with Christian Buil's ISIS software.

First, you have to configure the software (directory...):

An important step is the eShel configuration. I'm skiping this part as you are doing it only once, the instrument beeing very stable over time. This setup can be very time consuming as it does require to well align the camera - fortunatly ISIS does have some tools to help, as describered in Christian Buil ISIS tutorial oneShel data reduction. Here are my parameters:

First step is to acquire data, here is a copy of PRISM v10 software used for data acquisition of hd41117 reference star, with autoguiding ON:

Note that I have made a conversion tool in Libre Office Calc to get Be star status in BeSS (through ARASBeAm daily robot file) and display them as well as references (MILES) stars. I can easily display them in PRISM star chart to select my targets (Priority 1 or 2 usually) and the reference star:

Dark, bias and some standard parameter files are in CALIB subdirectory; I'm reusing them night after night...

I am acquiring a reference star spectrum (here: hd41117) which exists in MILES database, and with an elevation close to my targets (45-50° fopr that night). Flats (tungsten lamp only), LED (tungsten + LED) and Thorium-Argon frames aree taken using a PRISM script very useful (one click and it works!). Here is the script if it can be usful for others using PRISM:

REM Répertoire de sauvegarde des images

REM Penser à enlever la sauvegarde automatique dans PRISM avant de lancer le script!

sDirSave$="D:\Acquisitions\20160127 eShel101_Atik460 38420 Revel\"

Object$="hd41117"

PoseThAr=15000
PoseTung=700
PoseLEDs=700
ON=1
OFF=0
Port1=1
Port2=2
Port3=3
Port4=4

Switchdesired=1
// Recupere l'etat des swiches d'un coup dans une table
GETSWITCH Switchdesired nbSwitches ArrayName ArrayState

REM =================
REM Miroir + Tungsten
REM =================
SETSWITCH Port1 ON
Delay 1000
WaitForEndDelay
SETSWITCH Port4 ON
Delay 1000
WaitForEndDelay

For i=1 13
STR i i$
StartExposure_EX 2 PoseTung
sFullPath$=sDirSave$+Object$+"_tung-"+i$+".fits"
Print sFullPath$
WaitForEndExposure_EX 2
GetLastImageExposure_EX 2 img
SAVEFIT img sFullPath$
Close img
Next i

REM =================
REM LEDs + Tungsten
REM =================
SETSWITCH Port2 ON
Delay 1000
WaitForEndDelay

For i=1 3
STR i i$
StartExposure_EX 2 PoseLEDs
sFullPath$=sDirSave$+Object$+"_led-"+i$+".fits"
Print sFullPath$
WaitForEndExposure_EX 2
GetLastImageExposure_EX 2 img
SAVEFIT img sFullPath$
Close img
Next i

SETSWITCH Port2 OFF
Delay 1000
WaitForEndDelay

SETSWITCH Port4 OFF
Delay 1000
WaitForEndDelay

REM =================
REM ThAr
REM =================
SETSWITCH Port3 ON
Delay 1000
WaitForEndDelay

For i=1 3
STR i i$
StartExposure_EX 2 PoseThAr
sFullPath$=sDirSave$+Object$+"_thor-"+i$+".fits"
Print sFullPath$
WaitForEndExposure_EX 2
GetLastImageExposure_EX 2 img
SAVEFIT img sFullPath$
Close img
Next i

Delay 3000
WaitForEndDelay

SETSWITCH Port3 OFF
Delay 1000
WaitForEndDelay

SETSWITCH Port1 OFF
Delay 1000
WaitForEndDelay

Having taken spectra of this reference (hd41117) star, I can now process them in ISIS. I'm careful to rermove the "response" parameter as we will be using this star to create our own:

Double check the result of the processingn specially the resolving power per order and the number of orders redeuced (my goal is to process 23 orders, from #31 to #53).

The log can also be found in the file "_hd41117_20160127_784_full.log":

-------------- Paramètres d'entrée --------------
Objet : hd41117
Instrument : eShel_Atik460
Site : 38420 Revel
Observateur : Olivier Thizy
Répertoire de travail : D:\Acquisitions\20160127 eShel101_Atik460 38420 Revel\
Nom générique des spectres 2D : hd41117-
Nombre de spectres 2D bruts : 5
Fichier offset : offset
Fichier dark : dark
Ficher PRNU : prnu
Fichier tungstène : tung_hd41117
Fichier LED : led_hd41117
Fichier Thorium-Argon : thor_hd41117
Fichier cosmétique : cosme
Fichier de réponse spectrale (traitement global) : ri_hd41117
Décalage en vitesse : 0
Correction des rayons cosmiques non effectuée
Premier ordre analysé : 31
Dernier ordre analysé : 53
Largeur de la zone de binning : 24
Largeur de la boite de recherche des raies : 30
Nombre d'itération sélection des raies ThorAr : 4
Rang de l'ordre de référence : 34
Coordonnée Y de l'ordre de référence (centre image) : 873
Longueur d'onde de référence : 6583.906
Coordonnée X de la raie de référence : 586
Seuil de détection des ordres : 100
Angle alpha : 62.9
Angle gamma : 5.9
Nombre de traits au mm : 79
Nombre de pixels en X : 1374
Nombre de pixels en Y : 1099
Taille des pixels : 9.08
Focale : 85
Delta heure : 0
-------------------- Traitement --------------------
Nombre d'ordres trouvé : 25
Ordre #31 - Position : 920
Ordre #32 - Position : 903
Ordre #33 - Position : 886
Ordre #34 - Position : 868
Ordre #35 - Position : 849
Ordre #36 - Position : 830
Ordre #37 - Position : 810
Ordre #38 - Position : 789
Ordre #39 - Position : 768
Ordre #40 - Position : 746
Ordre #41 - Position : 723
Ordre #42 - Position : 699
Ordre #43 - Position : 675
Ordre #44 - Position : 650
Ordre #45 - Position : 623
Ordre #46 - Position : 596
Ordre #47 - Position : 568
Ordre #48 - Position : 539
Ordre #49 - Position : 508
Ordre #50 - Position : 476
Ordre #51 - Position : 442
Ordre #52 - Position : 409
Ordre #53 - Position : 374
Ordre #31 :   RMS = .0082   -   Nb. raies = 8
Ordre #32 :   RMS = .0134   -   Nb. raies = 10
Ordre #33 :   RMS = .0221   -   Nb. raies = 12
Ordre #34 :   RMS = .0067   -   Nb. raies = 12
Ordre #35 :   RMS = .0132   -   Nb. raies = 15
Ordre #36 :   RMS = .0049   -   Nb. raies = 16
Ordre #37 :   RMS = .0072   -   Nb. raies = 14
Ordre #38 :   RMS = .0098   -   Nb. raies = 15
Ordre #39 :   RMS = .0089   -   Nb. raies = 16
Ordre #40 :   RMS = .0104   -   Nb. raies = 15
Ordre #41 :   RMS = .0217   -   Nb. raies = 19
Ordre #42 :   RMS = .0211   -   Nb. raies = 16
Ordre #43 :   RMS = .0117   -   Nb. raies = 17
Ordre #44 :   RMS = .0068   -   Nb. raies = 15
Ordre #45 :   RMS = .0052   -   Nb. raies = 16
Ordre #46 :   RMS = .0102   -   Nb. raies = 15
Ordre #47 :   RMS = .0072   -   Nb. raies = 12
Ordre #48 :   RMS = .0030   -   Nb. raies = 12
Ordre #49 :   RMS = .0133   -   Nb. raies = 14
Ordre #50 :   RMS = .0110   -   Nb. raies = 11
Ordre #51 :   RMS = .0055   -   Nb. raies = 8
Ordre #52 :   RMS = .0115   -   Nb. raies = 11
Ordre #53 :   RMS = .0425   -   Nb. raies = 11
Resolution :
Order #31 : FWHM = 4.99 - Dispersion = .195 A/pixel - R = 7450.3
Order #32 : FWHM = 5.42 - Dispersion = .187 A/pixel - R = 6915.9
Order #33 : FWHM = 4.50 - Dispersion = .185 A/pixel - R = 8155.0
Order #34 : FWHM = 4.01 - Dispersion = .180 A/pixel - R = 9166.5
Order #35 : FWHM = 3.91 - Dispersion = .174 A/pixel - R = 9418.8
Order #36 : FWHM = 3.71 - Dispersion = .169 A/pixel - R = 9961.3
Order #37 : FWHM = 3.69 - Dispersion = .163 A/pixel - R = 10085.6
Order #38 : FWHM = 3.40 - Dispersion = .159 A/pixel - R = 10904.1
Order #39 : FWHM = 3.20 - Dispersion = .158 A/pixel - R = 11386.0
Order #40 : FWHM = 3.37 - Dispersion = .152 A/pixel - R = 10956.0
Order #41 : FWHM = 3.26 - Dispersion = .149 A/pixel - R = 11295.5
Order #42 : FWHM = 3.37 - Dispersion = .145 A/pixel - R = 10909.9
Order #43 : FWHM = 3.08 - Dispersion = .145 A/pixel - R = 11639.3
Order #44 : FWHM = 3.20 - Dispersion = .140 A/pixel - R = 11401.4
Order #45 : FWHM = 3.28 - Dispersion = .136 A/pixel - R = 11219.9
Order #46 : FWHM = 3.59 - Dispersion = .133 A/pixel - R = 10207.3
Order #47 : FWHM = 3.40 - Dispersion = .129 A/pixel - R = 10905.8
Order #48 : FWHM = 3.62 - Dispersion = .126 A/pixel - R = 10223.7
Order #49 : FWHM = 4.25 - Dispersion = .125 A/pixel - R = 8624.5
Order #50 : FWHM = 4.58 - Dispersion = .118 A/pixel - R = 8275.7
Order #51 : FWHM = 4.71 - Dispersion = .115 A/pixel - R = 8157.6
Order #52 : FWHM = 5.50 - Dispersion = .115 A/pixel - R = 6842.2
Order #53 : FWHM = 5.76 - Dispersion = .113 A/pixel - R = 6520.7
-------------- Paramètres de sortie --------------
Nom du profil de sortie : _hd41117_20160127_784_full
Date de prive de vue : 27/01/2016 18:48:35
Durée de prise de vue : 925.0
Durée de prise de vue décomposée : 5 x 180 s
Date de milieu de prise de vue : 27.789/01/2016
Jour Julien géocentrique du milieu de prise de vue : 2457415.2891

The profile shows a uncorrected but calibrated spectrum:

Open the database and look for MILES spectrum of that star (if it's not in MILES, then I'm using PICKLES but I usually prefere to use a MILES spectrum):

The profile shows our library spectrum which is different from our observfed one because of the "instrumental response":

Save it for exemple as "m_hd41117" (m for MILES) spectrum in your working directory:

Reload the observed spectrum (just clic on DISPLAY to reload it) and use the "Compare" tool in ISIS to compare it with the MILES library one. Make sure to display the "division":

After clicking ok, we have the division (Observed / Library) which is instrumental response polluted by some noise and lines.
Clic on "CONTINUUM" tool to smooth it but before smoothing it, remove the polluted area by double clicking before then double clicking after the area; do it for all the domains you can to exclude:

Select then the right smoothing parameter to get the final instrumental response:

Save the result in DAT format in your local directory:

Make sure to copy the ri_hd41117.dat instrumental response file from your working directory in your CALIB directory as this is where ISIS will be looking for it; then just rerun the data reduction but this time fill in the "response" parameter with that filename:

Et voilà - look at your profile, it's the fully reduced spectrum you can now share with others:

Of course, it is not that interesting to look for a reference star (but it can be useful to compare results, signal & noise levels...). So let's take other spectra, for exemple of 25 Ori - you can see the strong Halpha emission line:

Once acquisition is done, it's very easy and fast to reduce the spectrum by changing the filename root and object name in the eShel tab, and clic RUN:

Et hop! Here is ther final result:

Just compress in one ZIP file all the orders (#31 to #53) so it can be uploaded in BeSS database. Note that the FULL "_25ori_20160127_799_full.fits" file is the merged spectrum - but BeSS is looking for the order per order spectrum for eShel acquisition: