Desktop app reference

Every control of valerian-gui, with its range and default. The desktop app describes the window and the tutorial walks through a session. Command line: valerian-gui [FILE] opens FILE; -V and --version print the version and exit.

Top bar

Control	Does
Logo, name	The About page (F1).
File chip	The open file, its size and planes (wide windows only).
Recent	The last 8 images opened.
Night (F2)	Red night-vision palette. Default off; remembered.
GPU	Opens the GPU benchmark; a step on the rail leaves it.
Open (Ctrl+O)	Native file dialog for a FITS image.
About (F1, Esc closes)	Dedication, version, copyright, licence.

Rail

One button per step: Calibrate, Register, Stack, Process, Export. Status: Optional, Ready, Running, Waiting or Done (with a tick). Below 900 px wide only the numbers show.

View

Control	Does
Scroll, +, -	Zoom about the pointer, 5 % to 800 % of the preview.
Drag	Pan.
Percentage button, double click	Fit (never above 100 %).
Histogram	Show or hide it. Default shown; 128 bins, log scale, of what is drawn.
Dismiss	Hide a finished, cancelled or error message.
Cancel (Esc)	In the notice while Calibrate, Register, Stack, Drizzle, Star removal, Plate solve or Colour runs: stops the step. See Cancelling a step.

Cancelling a step

Control	Does
Cancel, in the notice	Asks the running step to stop. The button changes to "Cancelling..." and the headline to "Cancelling: finishing the frame in hand, nothing will be kept...". A second press does nothing.
Esc	The same as Cancel while a step runs and the About page is not open (Esc closes About first).
Where it applies	Calibrate, Register, Stack, Drizzle, Star removal, Plate solve and Colour. Writing a file (Save, Export, Apply and save) is short and has no Cancel.
How soon	At the next check: between files, between bands of a master frame, between frames while registering, warping or drizzling, between colour planes of a stack or of star removal, and between trial patches of sky in a plate solve. The frame or band in hand finishes first, so on large frames it can take a few seconds.
What is kept	Nothing. Calibrate, Register and Stack write into a hidden `.valerian-partial-<pid>` folder inside the output folder and move the files into place only when the whole run has finished, so a cancelled (or failed) run removes that folder, removes any output folder it had to create, and leaves files that were already there untouched.
What you see	A notice "Cancelled: calibration stopped. Nothing from the run was kept." (registration, stacking, drizzling, star removal, plate solving or colour calibration in the same words) with Dismiss. It is not shown as an error. The step's panel returns to its idle button and the rail row leaves "Running"; the result of an earlier run of the step is kept.
If the step finishes first	Cancel arrives after the last check and the step completes normally; its result is kept.

Calibrate

Control	Default	Does
Lights	empty	Folder or file of lights. Required.
Darks, Flats, Dark flats, Bias	empty	Folder, or one master file. At least one of darks, flats and bias is needed.
Calibrated frames go to	beside the lights, `calibrated`	Output folder; masters go in `masters/`.
Calibrate lights		Runs. Fixed: automatic rejection, hot 40 and cold 12 sigma, dead below 0.2 of the flat, global flat normalisation, 1 GiB memory.

Register

Control	Default	Does
Frames	Calibrate output	Folder of frames.
Aligned frames go to	`registered` beside it	Output folder.
Register frames		Best frame as reference, default detection, no level matching; raw colour is demosaiced.

Stack

Control	Default	Does
Mean, Drizzle	Mean	Chooses the stack or the drizzle.
Frames	last step's output	Folder of frames.
Stack goes to	`stack.fits` beside it	The output file; the stack is opened afterwards.
Rejection	Automatic	Automatic (by frame count), Winsorised, Sigma (3 sigma both sides), None.
Stack frames		Runs on the CPU engine.

Drizzle

Control	Range	Default
Frames, Choose folder...	folder	empty
Scale	1 to 4, step 0.5	2
Pixfrac	0.2 to 1.0	0.6
Reject outliers	on or off	on
Rejection (sigma)	2 to 8	4
Drizzle frames, Save drizzled, Open it, Save as...

Process

Image box, Browse..., Open: the working image. Chips: Stretch, Star removal, Plate solve, Colour.

Stretch

Control	Range	Default
Curve	Auto, MTF, Arcsinh, GHS	Auto
Sky target (Auto)	0.02 to 0.5	0.10
Midtone (MTF)	0.001 to 0.999	0.25
Strength (Arcsinh)	0.5 to 5000, logarithmic	50
Stretch factor (GHS)	0 to 6	3.0
Local intensity	-5 to 15	0
Symmetry point	0 to 1	0
Shadow protection	0 to the symmetry point	0
Highlight protection	symmetry point to 1	1
Set black and white by hand	on or off	off
black, white	any (drag values)	measured
Black below sky (sigma)	0 to 6	2.8
White percentile	99 to 100	99.995
Same stretch for every colour plane	on or off	on
Reset		Auto curve
Save as..., Apply and save		`<name>_stretched.fits`

Star removal

Control	Range	Default
Threshold (sigma)	2.5 to 12	4.0
Mask size	0.5 to 3	1.0
Grow (px)	0 to 10	1.5
Largest radius (px)	5 to 150	60
Add noise to the filled pixels	on or off	on
Remove stars		Runs on the full image.
Starless, Original, Stars, Mask		Which layer is drawn.
Strength	0 to 1	1 (applied after the run)
Save starless and stars		`<name>_starless.fits` and `<name>_stars.fits`

Plate solve

Control	Range	Default
RA, Dec	degrees or dd:mm:ss	from the header
Search radius (deg)	0.1 to 5	1.0
Blind: search the whole sky	on or off	off
arcsec per pixel	0.1 to 60	from the header; searched 15 % either way
Catalogue, Choose catalogue...	`.vcat` file	`gaia-dr3-g11.vcat` beside the program
Solve, Save with WCS		`<name>_solved.fits`

Colour

Control	Range	Default
Neutral at BP-RP	0.3 to 1.5	0.82
Brightest (G)	4 to 10	6
Faintest (G)	8 to 11	11
Aperture (FWHM)	1 to 4	2
Make the background neutral	on or off	on
Calibrate colour		Needs three planes and a plate solution.
Calibrated, Original		Which picture is drawn.
Save calibrated		`<name>_calibrated.fits`

Export

Control	Default	Does
Format	FITS	FITS: 32-bit float, unstretched, with header. PNG: 8-bit with the current stretch.
Save as...	`<name>_export.fits`	The extension follows the format.
Export picture		Writes it.

GPU

Control	Range	Default
Adapter	Hardware, Software	Hardware
Width, Height (px)	256 to 6144, 256 to 4608	2048, 1536
Frames in the combine	3 to 32	12
Run benchmark		Times each kernel against the CPU.

Settings file

$VALERIAN_GUI_CONFIG, else %APPDATA%\valerian\gui.conf on Windows, else $XDG_CONFIG_HOME/valerian/gui.conf, else ~/.config/valerian/gui.conf. Plain key=value: window=WxH, night=1, and up to eight recent= paths.

Keyboard shortcuts

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