The goal of this page is to explain my methods for processing astronomy images. The IRIS software is so difficult to use and poorly userfriend at the beginning that it seemed to me useful to do a tutorial for you.
If you have questions, suggestions, or if this page was useful to you, don't hesitate to send a message to me.
- Processing images of the deep sky in case of LRGB: camera + filter wheel
- Organizing your directories
- Setting up IRIS
- Building the offset image
- Building the dark image
- Building the flat image
- Pre-processing the images of the L filter
- Pre-processing the images of the R, G and B filters
- Assembling the images of the L, R, G and B filters
- Processing the images of deep sky in case of using a reflex camera
- Processing the images of planets in LRGB
- Processing images of the deep sky in case of LRGB: camera + filter wheel
- Organizing your directories I first advise you to organize your images and put them in directories in order to avoid errors and facilitate the images selection.
- Initial set up of IRIS software Go to menu "Fichiers -> réglages", click on "FIT", and select a working directory, which you should avec previously created:
- Building the offset image
- Select the offset files in binning x1
- Building the dark image
- Select the dark files in binning x1
- Building the flat image
- Select the flat images for L filter
- Build the flat image for the R filter
- Build the flat image for the G filter
- Build the flat image for the B filter
- Pre-processing the L filter image
- Check the quality of each image taken with L filter
- Select the files of the images taken with L filter
- Générique d'entrée: l
- Carte Offset: offsetbin1
- Carte Dark: darkbin1
- Carte Flat-field: flatl
- Fichier cosmetique: cosmebin1
- Générique de sortie: i
- Nombre: this number will fill in automatically with the number of images which you had selected for L filter
- Uncheck the box "Optimisation"
- Registrate the images
- Nom générique d'entrée: i
- Nom générique de sortie: r
- Mode d'alignement: Appariement 1 zone (transformation linéaire)
- Check "sélection de la zone"
- Pre-processing images of filters R (red), G (green) and B (blue)
- Check the quality of each image
- Select the files of the images of the object taken with one of the filters (R for example)
- Générique d'entrée: letter of the filter: r,g or b
- Carte Offset: offsetbin2
- Carte Dark: darkbin2
- Carte Flat-field: flat of the filter: flatr, or flatg, or flatb
- Fichier cosmetique: cosmebin2
- Générique de sortie: i
- Nombre: this number is automatically filled with the number of images you had selected for the current filter
- Unckeck the box "Optimisation"
- Registrate the images
- Nom générique d'entrée: i
- Nom générique de sortie: r
- Mode d'alignement: Appariement 1 zone (transformation linéaire)
- Cochez "sélection de la zone"
- Resizing the image
- Merginig the images of filters L, R, G and B
- Assembling the images
- In the window "Seuils de visualisation", click on "Auto", and move the cursors to improve the display
- Enter the value "1" in each entry field "Pas"
- Select a filter by checking it, for example "Rouge", then make the red layer move with the up, down, left and right arrows. Watch a star, and the goal is to merge the 4 layers. Move each layer with the same procedure in order to merge them.
- Processing deep sky images incase of using a reflex camera
- Processing images of planets in LRGB
Here is an example, where I have one directory per year, the for each night I have a dated directory, then one directory for darks, one for offsets, one for flats, and for each object one directory per filter:
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At this time IRIS disappears and goes to the background. You need to open your directory where files are stored using the windows file exporer, and select your files, then drag them to the IRIS windows, thanks to the IRIS icon in the bottom bar. Don't forget to first select the image type FIT in IRIS:
Then enter "o" as generic name, and click on "Création de la liste". A the end of the process, click on "Fermer".
The IRIS displays a small window showing the number of selected images, here 15 in the example.
Then select the menu "Prétraitement -> Faire un offset..." :
Then enter the generic name "o", and click on "OK":
At the end of the process, if the command line window is not displayed, click on the command line icon:
In this new small window, enter the command line "save offsetbin1" and user the enter key. You will see the file name displayed at the top, which means that it was well saved.
There you are, your offset image in binning x1 is ready for next steps.
Redo the same processing sequence for offsets in binning x2, then save at the end with the name offsetbin2: "save offsetbin2".
Then enter "d" as generic name, and click on "Création de la liste". At the end of the process, click on "Fermer".
Then IRIS will display a small window showing the number of selected images, here 8 in the example.
Then select the menu "Prétraitement -> Faire un dark..." :
Then enter the generic name "d", enter the offset offsetbin1, and click on "OK":
Then in the command line window, enter "save darkbin1" to save the dark image. Then enter the command line: find_hot cosmebin1 200
IRIS displays then in the small window "Sortie" the number of hot pixels found, for example 140.
Change the number from 200 to 100 and press the enter key, IRIS will display a new number of hot pixels found.
Repeat this action until IRIS displays the error message "Nombre de points chauds limité à 10000".
Increase again the number, until IRIS displays the maximum number of hot pixels found without generating the error message.
It will save automatically a file named cosmebin1.fit containing the list of hot pixels.
Repeat all this process for dark images in binning x2, then save as "save darkbin2", and "find_hot cosmebin2 xx".
At the end of this process, you have built the dark image in binning x1, in binning x2 and the list of corresponding hot pixels.
More to come...
Then enter "f" as generic name, and click on "Création de la liste". At the end of the process, click on "Fermer".
Then IRIS displays a small window showing the number of selectd images, here 15 in the example.
Click on "Auto" in the window "Seuils de visualisation", to watch the flat image.
Then select the menu "Prétraitement -> Faire un flat-field..." :
Then enter the generic name "f", and enter the offset offsetbin1 (because the L filter is taken in binning x1), enter 15000 as the normalization value for the Atik 314L+, and click "OK":
Click on "Auto" in the window "Seuils de visualisation", so watch the flat image.
Puis dans la fenêtre de saisie des commandes, taper "save flatl" pour sauvegarder l'image de flat.
Redo the same procedure as for L filter, but be careful to use offsetbin2 instead of offsetbin1, because the main image is taken in binning x2 with the red filter.
Enter "save flatr" at the end of the process.
Redo the same procedure as for L filter, but be careful to use offsetbin2 instead of offsetbin1, because the main image is taken in binning x2 with the green filter.
Enter "save flatg" at the end of the process.
Redo the same procedure as for L filter, but be careful to use offsetbin2 instead of offsetbin1, because the main image is taken in binning x2 with the blue filter.
Enter "save flatb" at the end of the process.
Open each file of image taken with the L filter, in order to check the quality of the image. Check that stars are like points. If the image is not good, it will not be used for next steps.
To open a file, go to menu "Fichier -> Charger":
Then select a file of an image of the object taken with L filter, and double click on it:
When the image is loaded in IRIS, click on the "Auto" button of the "Seuils de visualisation" window. Then watch the stars to ckeck if they are well round and not elongated, which prooves that the guiding was good.
Example where the image will not be used. You will have to decide yourself the threshold of maximum defaults that you accept:
Once you have checked each image, you will be able to process the ones you kept. You can move the unwanted images to a special directory, in order to avoid mistakes.
Then IRIS will display a smalll window showing the number of selected images, here 13 in the example.
Click on "Auto" in the window "Seuils de visualisation", to watch the image.
Then select the menu "Photo numérique -> Prétraitement..." :
In the window, enter the data:
At then end of the process, click on "Auto" in the window "Seuils de visualisation", to watch the image.
The goal of the registration process is to align the images so that they can be added later, and they are exactly superposed.
In IRIS, I use the registration method by selecting a zone having with stars only, not too far from the center of the image.
Click first on "x1", then make a square around several stars with your mouse:
Then select the menu "Traitement -> Registration des images stellaires..."
In the dialog window, enter:
While the registration process is going on, you will see the surrounded stars:
Then select the menu "Traitement -> Addition d'une séquence..."
Then when the process is over, click on "Auto" in the window "Seuils de visualisation"
Then select the menu "Fichier -> Informations image...", and read in the window "Sortie" the size of the image. Here in the example it is 1391x1039 pixels.
Then select the menu "Géométrie -> Fenêtrage":
Then enter a Xmax and a Ymax a little bit lower than the size of the image and rounded. This action will allow later to have images of exactlty the same size for all filters, because regarding those having different binning, you will have to change the scale. Here in the example I enter Xmax=1380 et Ymax=1030.
Then save the image by entering the name of the object followed by the filter name :"save m63l"
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The process is similar to that of L filter, so you can follow the same steps, but you need to use the offset images, dark and flat in binning x2, and the right flat for each filter.
There are some changes at the end of the process for scaling.
Like for L filter, open each file of the object image, in order to check the quality of the image. Check that stars are well rounded. If the image is not good, don't use it for next steps.
To open a file, go to menu Fichier -> Charger:
Then select a file of the object image, and double click on it.
When the image is loaded into IRIS, click on the "Auto" button of the window "Seuils de visualisation". Then watch the stars to ckeck they are well rounded and elongated, which prooves that the guiding was good.
Once you have check each image, you will be able to process the ones that you have kept. You can move the unwanted images in a special directory to avoid mistakes.
Then IRIS displays a small window showing the number of selected images.
Click on "Auto" in the window "Seuils de visualisation", to watch the image.
Then select the menu "Photo numérique -> Prétraitement..." :
In the window, enter the data:
At the end of the process, click on "Auto" in the window "Seuils de visualisation", to watch the image.
The goal of the registration process is to align the images so that they can be added later, and they are exactly superposed.
In IRIS, I use the registration method by selecting a zone having with stars only, not too far from the center of the image.
Click first on "x1", then make a square around several stars with your mouse.
Then select menu "Traitement -> Registration des images stellaires..."
In the dialog window, enter:
While the registration process is going on, you will see the surrounded stars
Then select menu "Traitement -> Addition d'une séquence..."
Then when the process is over, click on "Auto" in the window "Seuils de visualisation"
For filters R, G and B, you will have an image with less pixels, because they were taken in binning x2. So you must change the scale of these images. To do so, select the menu
Then check the method "Spline (doux)", and click on OK:
Then select the menu "Géométrie -> Fenêtrage":
Then enter a Xmax and a Ymax equal to those used for L filter. Here I enter Xmax=1380 and Ymax=1030.
Then save the image by entering the object name followed by the name of the filter: "save m63r", "save m63v", or "save m63b"
Select menu "Visualisation -> (L)RGB...":
Then enter the name of the images of each filter and check the box for the L filter, and click on "Appliquer". At this time, you see the 4 images appear superposed, and as they are not exactly at the same place, you can see that the stars have 4 separated images for the luminance (white), the red, green and blue.
Puis :
Then click on "OK", and once more on "Auto" in the window "Seuils de visualisation". Go back to the top left of the image with the scrolling bar on the right.
In the command window, enter "win" then the enter key. At this time the cursor of the mouse changes to a double cross. You must click at the top left of the image then at the bottom right, to define the zone which is good and remove the bad edges.
Then make a rectangle with the mouse in a place where there is no star, and where the sky is supposed to be the most dark of the image.
Then enter the command line "black" and press the enter key:
Then click again on "Auto" in the window "Seuils de visualisation", and play with the cursors to have a quite good image, with the center of the galaxy not to saturated.
Then save your first image, by entering the command line "save m63-1"
Select the menu " -> Rehaussement de la dynamique (DDP)...", and play with the cursors, then click on "OK".
Adjust the gamma:
More to come...
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