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=Siril processing tutorial=
<!--T:20-->
<span style="color: #ff0090; font-weight: bold; text-align: center; margin: 2em; font-size: 125%;">This page is the old documentation for early versions of Siril 0.9. Please refer to the new documentation on [https://siril.readthedocs.io/en/stable/ siril.readthedocs.io] or the new tutorials on [https://siril.org/tutorials siril.org] instead.</span>


=Siril processing tutorial= <!--T:1-->
<!--T:2-->
* [[Siril:Tutorial_import|Convert your images in the FITS format Siril uses (image import)]]
* [[Siril:Tutorial_import|Convert your images in the FITS format Siril uses (image import)]]
* [[Siril:Tutorial_sequence|Work on a sequence of converted images]]
* [[Siril:Tutorial_sequence|Work on a sequence of converted images]]
* [[Siril:Tutorial_preprocessing|Pre-processing images]]
* [[Siril:Tutorial_preprocessing|Pre-processing images]]
* &rarr; '''Registration (PSF image alignment)'''
* &rarr; '''Registration (Global star alignment)'''
* [[Siril:Tutorial_stacking|Stacking]]
* [[Siril:Tutorial_stacking|Stacking]]


==Registration (PSF image alignment)==
==Registration (Global star alignment)== <!--T:3-->
 
Siril has two automatic registration tools. In this example we will use the PSF one. Currently, only translation is used for image alignment, no rotation.


The first step is to load the sequence, if we continue this tutorial this will be the debayer_M8-M20 sequence. Go back to the sequence tab, and click on "search sequence" to find the new sequence created by the pre-processing. Select the debayer_ sequence, which will open the image preview windows if not already opened, and display the first image of the sequence.
<!--T:4-->
Siril has four automatic registration tools. In this example we will use the all automatic one: Global star alignment. This method is dedicated to the deep-sky registration, and contrary to the One Star registration, it handles the rotation of images between each others.


From this tab, you can change the image being viewed in the grey and colour windows, include or exclude them from a user-defined selection that will later be used to indicate which files should be stacked or not, and set the reference image. While browsing through the images of the sequence, a reference image may be set to a specific image if you think it has a better quality than the others, or if it's best centred. Note that when the reference image is set, it will be saved in the sequence and it will be opened first when loading the sequence the following time.
<!--T:5-->
After debayering (in previous step), the new sequence is loaded and you can check it in the "image sequences" tab. From this tab, you can change the image being viewed in the grey and colour windows, include or exclude them from a user-defined selection that will later be used to indicate which files should be stacked or not, and set the reference image. While browsing through the images of the sequence, a reference image may be set to a specific image if you think it has a better quality than the others, or if it's best centred. Note that when the reference image is set, it will be saved in the sequence and it will be opened first when loading the sequence the following time.


An alternative to the use of buttons of the sequence tab is to use the ''sequence list''. Double click on the grey window to make it appear:
<!--T:7-->
An alternative to the use of buttons of the sequence tab is to use the ''sequence list''. Click on the dedicated button [[File:Siril_button_seq.png|24px|frameless|link=|middle]].


<!--T:8-->
[[File:Siril sequence list.png|700px]]
[[File:Siril sequence list.png|700px]]


You can then open an image of the sequence by double-clicking on its line, and select (include or exclude) the image from the sequence by checking or unchecking its box. X Y and quality columns will be displayed later, when registration data is available.
<!--T:9-->
To make registration, just click on "Go Register" button. Everything will be automatic. The algorithm tries to match triangle patterns in order to align images and you can check each step of registration in the console output.


To do the automatic registration, select a isolated star in a grey image, preferably in the same layer than the layer used for registration (green by default) to be sure that the star appears in this layer, and click the "Go register" button. Also, make sure that the selection is large enough to include the star on every frame but not too large to avoid computing PSF of another star as you can see on the second image below.
<!--T:16-->
[[File:Siril_global_star_reg.png|700px]]


[[File:Siril registration done area selected.png|700px]]
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A new sequence will be created and automatically loaded at the end of the process. In addition, an average of FWHM is computed and provided in this sequence. It is thus possible to select best images for stacking.


[[File:Siril area_selected.png|700px]]
<!--T:18-->
===Special cases with low sigma/noise ratio===
In some cases, due to high noise level, automatic registration gives wrong results by confusing noise and stars during star detection. To overcome this issue, Siril provides parameters adjustable parameters offering a better tool detection. These parameters are located in the Dynamic PSF window.
[[File:Siril_PSF_param.png|700px]]


You can view the registration data in the list on the left when you are viewing the layer corresponding to the registration layer. You can also see in the image above that the reference image is on the yellow line and the currently displayed image has its name in bold. Take as reference the image with the lowest FWHM: this image is given by Siril in the console output.
<!--T:19-->
In our case, increasing thershold value will give better results.


[[File:Siril registratio_done.png|700px]]


<!--T:15-->
Next item of the tutorial: [[Siril:Tutorial_stacking|Stacking]].
Next item of the tutorial: [[Siril:Tutorial_stacking|Stacking]].


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Latest revision as of 22:40, 16 September 2023

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This page is the old documentation for early versions of Siril 0.9. Please refer to the new documentation on siril.readthedocs.io or the new tutorials on siril.org instead.

Siril processing tutorial

Registration (Global star alignment)

Siril has four automatic registration tools. In this example we will use the all automatic one: Global star alignment. This method is dedicated to the deep-sky registration, and contrary to the One Star registration, it handles the rotation of images between each others.

After debayering (in previous step), the new sequence is loaded and you can check it in the "image sequences" tab. From this tab, you can change the image being viewed in the grey and colour windows, include or exclude them from a user-defined selection that will later be used to indicate which files should be stacked or not, and set the reference image. While browsing through the images of the sequence, a reference image may be set to a specific image if you think it has a better quality than the others, or if it's best centred. Note that when the reference image is set, it will be saved in the sequence and it will be opened first when loading the sequence the following time.

An alternative to the use of buttons of the sequence tab is to use the sequence list. Click on the dedicated button .

To make registration, just click on "Go Register" button. Everything will be automatic. The algorithm tries to match triangle patterns in order to align images and you can check each step of registration in the console output.

A new sequence will be created and automatically loaded at the end of the process. In addition, an average of FWHM is computed and provided in this sequence. It is thus possible to select best images for stacking.

Special cases with low sigma/noise ratio

In some cases, due to high noise level, automatic registration gives wrong results by confusing noise and stars during star detection. To overcome this issue, Siril provides parameters adjustable parameters offering a better tool detection. These parameters are located in the Dynamic PSF window.

In our case, increasing thershold value will give better results.


Next item of the tutorial: Stacking.

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