Siril command line functions reference

This manual is a summary of the different commands you can find in Siril. As Siril is in alpha test phase, numerous commands can be added and some others can be changed. Please check the date of the page (the history link) before using.

The <SPACE> character is the delimiter between arguments. If you need to have spaces inside the arguments, you can use the quote or double quote, just like in a shell.


addmax filename

addmax compute a new image IMG with IMG_1 and IMG_2. The pixel of IMG_1 is replaced by the pixel at the same coordinates of IMG_2 if the intensity of 2 is greater than 1. Do not forget to save the result.



Returns the background level of the image loaded in memory.



Returns the background noise level.


cd directory

Set the new current working directory. directory can contain the ~ token, expanded as the home directory, directories with spaces in the name can be protected using single or double quotes. Examples:

  • cd ~/M42
  • cd '../OIII 2x2/'



Return the coordinates of the center of gravity of the image.



Clear all the stars saved in memory and displayed on the screen.


crop x, y, width, height

Crops the current image within the rectangle previously selected.


cosme filename

Apply the local mean to a set of pixels on the in-memory image (cosmetic correction). The coordinate of this pixels are in an ASCII file [list file]. COSME is adapted to correct residual hot and cold pixels after preprocessing.
The line P x y type will fix the pixel at coordinates (x, y) type is an optional character (C or H) specifying to Siril if the current pixel is cold or hot. This line is created by the command find_hot but you also can add some lines manually.
The line C x 0 type will fix the bad column at coordinates x.
The line L y 0 type will fix the bad line at coordinates y.


cosme_cfa filename

Same function that COSME but applying to RAW CFA images.


ddp level coef sigma

Performs a DDP (digital development processing) as described first by Kunihiko Okano. This implementation is the one described in IRIS. It combines a linear distribution on low levels (below level) and a non-linear on high levels. It uses a Gaussian filter of sigma sigma multiplies the resulting image by coef. The typical values for sigma are included between 0.7 and 2



Computes the entropy of the opened image on the displayed layer, only in the selected area if one has been selected or in the whole image else. The entropy is one way of measuring the noise or the details in an image.



Quits the application.


extract NbPlane

Extracts NbPlane Planes of Wavelet domain.


fdiv filename scalar

Divides the image in memory by the image given in argument. The resulting image is multiplied by the value of the scalar argument. Please check that the image is in the working directory. See also idiv.


fftd modulus phase

Applies a Fast Fourier Transform to the image loaded in memory. Modulus and phase given in argument are saved in FITS files.


ffti modulus phase

This function is used to retrieve corrected image applying an inverse transformation. The modulus and phase used are the files given in argument.


fill value x y width height

Fills the whole current image (or selection) with pixels having the value intensity.


fill2 value x y width height

Same command than fill but this is a symmetric fill of a region defined by the mouse. Used to process an image in the Fourier (FFT) domain.


find_hot filename cold_sigma hot_sigma

The command provides a file lists "filename" (format text) in the working directory which contains the coordinates of the pixels which have an intensity "hot_sigma" times higher and "cold_sigma" lower than standard deviation. We generally use this command on a master-dark file.



Detects stars having a level greater than a threeshold computed by Siril. The algorithm is based on the publication of Mighell, K. J. 1999, in ASP Conf. Ser., Vol. 172, Astronomical Data Analysis Software and Systems VIII, eds. D. M. Mehringer, R. L. Plante, & D. A. Roberts (San Francisco: ASP), 317.

After that, a dynamic PSF is applied and Siril rejects all detected structures that don't fulfill a set of prescribed detection criteria. Finaly, a circle is drawn around detected stars. See also the command clearstar.


fmedian ksize modulation

Performs a median filter of size ksize [math] \times[/math]ksize (ksize MUST be odd) to the original image with a modulation parameter modulation. The output pixel is computed as : out [math]=[/math]mod [math] \times\ m + (1-[/math]mod[math]) \times [/math]in, where m is the median-filtered pixel value. A modulation's value of 1 will apply no modulation.


fixbanding amount sigma

Try to remove the canon banding. "Amount" define the amouont of correction. Sigma defines a protection level of the algorithm, higher sigma gives higher protection.


gauss sigma

Performs a Gaussian filter with the given sigma.



Gives the available commands.


histo layer

Calculates the histogram of the image layer in memory and produces file histo_[layer name].dat in the working directory.

layer = 0, 1 or 2 with 0=red, 1=green and 2=blue.


iadd filename

Adds the image in memory to the image designed in argument. Please check that the image is in the working directory.


idiv filename

Divides the image in memory by the image given in argument. Please check that the image is in the working directory. See also fdiv.


imul filename

Multiplies the image in memory by the image given in argument. Please check that the image is in the working directory.


isub filename

Substracts the image in memory by the image given in argument. Please check that the image is in the working directory.


load filename
load filename.ext

Loads the fits image filename; it first attempts to load filename, then and finally filename.fits and after, all supported format, aborting if none of these are found. These scheme is applicable to every Siril command implying reading files. Fits headers MIPS-HI and MIPS-LO are read and their values given to the current viewing levels.

Writing a known extension at the end of filename will load the image filename.ext: this is used when numerous files have the same name but not the same extension.

Extensions supported are :

  • *.fit, *.fits, *.fts
  • *.bmp / *.jpg, *.jpeg / *.png / *.tif, *.tiff
  • *.ppm, *.pgm
  • *.pic (IRIS file)



Computes and applies a logarithmic scale to the current image.



This command lists files and diretories in the working directory.



Rotates the image around a vertical axis.



Rotates the image around an horizontal axis.


new width height nb_layers

Creates a new image filled with zeros with a size of width x height. The image is in 16-bit format, and it contains nb_layers layers, nb_layers being 1 or 3. It is not saved, but displayed and can be saved afterwards.


nozero level

Replaces null values by level values. Useful before an idiv or fdiv operation.


offset value

Adds the constant value to the current image. This constant can take a negative value. As Siril uses unsigned fit files, if the intensity of the pixel become negative its value is replaced by 0 and by 65535 (for a 16-bit file) if the pixel intensity overflows. To check the minimum and maximum intensities values, click on the Auto level button and note the low and high threshold.



Make a selection around a star and call the command PSF. It will give you:

  • The centroid coordinates (x0 and y0) in pixel units, which is the position of the center of symmetry of the fitted PSF.
  • The FWHM on the X and Y axis.
  • The rotation angle of the X axis with respect to the centroid coordinates.
  • The average local background.
  • The maximal intensity of the star: this is the peak value of the fitted function, located at the centroid coordinates x0 and y0.
  • The relative magnitude of the star.
  • The RMSE. This is an estimate of fitting quality. The smaller the RMSE is, the better the function is fitted.

To be relevant, the selection MUST be done on a non-saturated star.



Same command than psf but works for sequences. Results are dumped in the console in a form that can be used to produce brightness variation curves.


resample factor

Resample image with a factor "factor"


rmgreen type

rmgreen is a chromatic noise reduction filter. It removes green noise in the current image. This filter is based on PixInsight's SCNR Average Neutral algorithm and it is the same filter used by HLVG plugin in Photoshop. In command line, the lightness is always preserved. For image processing without L* preservation use the graphical tool box and uncheck the corresponding button.

Type=1 stands for Average Neutral Protection, while type=2 stands for Maximum Neutral Protection.


rotate degree

Rotates the image of an angle of degree value. This function requieres the installation of libopencv.



Rotates the image of an angle of 180° around its center. This is equivalent to the command "rotate 180" or "rotate -180".


satu coeff

Enhance the global saturation of the image. Try iteratively to obtain best results. For example: satu 0.1


save filename

Save current image to Fits headers MIPS-HI and MIPS-LO are added with values corresponding to the current viewing levels..


savebmp filename

Save current image under the form of a bitmap file with 8bits per channel: filename.bmp (BMP 24 bits). This function is like a screenshot of what you see with the levels updated. This is very usefull to share an image in the bitmap format.


savejpg filename [quality]

Save current image into a JPG file. You have the possibility to adjust the quality of the compression. A value 100 for quality parameter offers best fidelity while a low value increases the compression ratio. If no value is specified, it holds a value of 100. This command is very usefull to share an image in the jpeg format on the forums for example.


savepnm filename

Save current image under the form of a Netpbm file format with 16bits per channel. The extension of the output will be filename.ppm for RGB image and filename.pgm for gray-level image. More details about the Netpbm format at :


savetif filename

Save current image under the form of a uncompressed TIFF file with 16bits per channel.


savetif8 filename

Same command than savetif but the output file is saved in 8bits per channel.


select from to

This command allows easy mass selection of images in the loaded sequence (from - to, to included). Examples:

select 0 0

selects the first.

select 1000 1200

selects 201 images starting from number 1000

The second number can be greater than the number of images to just go up to the end.


setcpu number

Defines the number of processing threads used for calculation. Can be as high as the number of virtual threads existing on the system, which is the number of CPU cores or twice this number if hyperthreading (Intel HT) is available.


setmag magnitude

Calibrates the magnitude by selecting a star and giving the known apparent magnitude. All PSF computations will return the calibrated apparent magnitude afterwards, instead of an apparent magnitude relative to ADU values. To reset the magnitude constant see unsetmag.


setmagseq magnitude

This command is only valid after having run seqpsf or its graphical counterpart (select the area around a star and launch the psf analysis for the sequence, it will appear in the graphs). This command has the same goal as setmag but recomputes the reference magnitude for each image of the sequence where the reference star has been found. When running the command, the last star that has been analysed will be considered as the reference star. Displaying the magnitude plot before typing the command makes it easy to understand. To reset the reference star and magnitude offset, see unsetmagseq.


split r g b

The command splits the color image into three distincts files (one for each color) and save them in r g and b file.



Returns global statistic of the current image. If a selection is made, the command returns global statistic within the selection.



Opens all sequences in the CWD and stacks them with the sum stacking.

threshlo, threshhi, thresh

These are threshold functions:

  • threshlo 40 replaces values below 40 with 40;
  • threshhi 1000 replaces values above 1000 with 1000;
  • thresh 40 1000 does both.


unselect from to

This command allows easy mass unselection of images in the loaded sequence (from - to). See select.



Reset the magnitude calibration to 0. See setmag.



Reset the magnitude calibration and reference star for the sequence. See setmagseq.


unsharp sigma multi

Applies to the working image an unsharp mask with sigma sigma and coefficient multi.


visu low high

Displays an image with low and high as the low and high threshold.


wavelet plan_number type

Computes the wavelet transform on plan_number plans using linear (type=1) or bspline (type=2) version of the 'a trous' algorithm. The result is stored in a file as a structure containing the planes, ready for weighted reconstruction with wrecons.


wrecons c1 c2 ... cn

Reconstructs to current image from the planes previously computed with waveletand weighted with coefficients c1, c2, ..., cn according to the number of planes used for wavelet transform