Detailed Documentation on Astro Live Stacker

Reference documentation

Thu, 11 Jun 2026 00:33:38 +0000

Overview

This section contains detailed documentation about ALS bits and bolts

🧠 It elaborates on the concepts introduced at the beginning of the user guide

Modules and Processes

Thu, 11 Jun 2026 00:33:38 +0000

Overview

In here, you will find detailed documentation about ALS modules and processes.

From what a module is to how a process works, you will find everything you need to know about the bits and bolts of ALS.

Modules

An ALS module is an elaborated processing unit responsible for a specific task.

It has its own engine
It can be started and stopped at will
It has access to the settings defined in ALS preferences
Its behavior can be controlled through the ALS interface

Modules are dumb and isolated. They have no knowledge of other parts of the application. They just do their job and report to the application

Scanner

Thu, 11 Jun 2026 00:33:39 +0000

Overview

The Scanner module is the entry point for your subs in ALS.

It is responsible for:

Monitoring the appearance of subs in the scan folder
Loading the detected subs

ℹ️ Existing files are ignored

Files present in the scan folder before the Scanner module is started are not detected

ℹ️ Detection of subs is recursive

Subs are detected regardless of the level of subfolders where they appear within the scan folder

Preprocess

Thu, 11 Jun 2026 00:33:38 +0000

Overview

The Preprocess pipeline handles calibration processes

Configuration

The Preprocess pipeline itself requires no configuration.

The configuration of the calibration processes is managed by the processes themselves. See the Behavior section below.

Control

The Preprocess module is launched in the background at ALS startup

Source	Type	Response
sub(s) in queue	Event	trigger calibration

Input

Data	Type
sub at queue front	Image

Behavior

Performs calibration processes on the sub:

Output

Calibrated sub is broadcast

Hot Pixel Removal

Thu, 11 Jun 2026 00:33:39 +0000

Overview

The HotPixelRemove process removes hot pixels from the image.

Its configuration is managed via ALS preferences.

Configuration

	Source	Data Type	Required	Default
ON/OFF	Preferences: Processing Tab	ON/OFF	∅	OFF

Control

This process is controlled by the Preprocess pipeline.

Input

Data	Type
image provided by the Preprocess pipeline	Image

Behavior

graph LR

START([START])

TEST_ENABLED{{Process enabled?}}
TEST_COLOR{{Color image?}}

COMPUTE[Compute average value of neighbors of each pixel]
REPLACE[Replace hot pixel value with the average of its neighbors]

RETURN[Return modified image]
UNCHANGED[Return unchanged image]

END([END])

START --> TEST_ENABLED
TEST_ENABLED -->|Yes| TEST_COLOR
TEST_COLOR ---->|Yes| UNCHANGED
TEST_ENABLED ---->|No| UNCHANGED
TEST_COLOR -->|No| COMPUTE
COMPUTE --> REPLACE
REPLACE --> RETURN
RETURN --> END
UNCHANGED --> END

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class START bounds
class TEST_ENABLED test
class TEST_COLOR test
class COMPUTE step
class UNCHANGED step
class REPLACE step
class RETURN step
class END bounds

Each pixel in the image whose value deviates too much from its neighbors is considered a hot pixel.

Dark Subtraction

Thu, 11 Jun 2026 00:33:38 +0000

Overview

The DarkRemove process subtracts the thermal noise from the image using a user-provided master dark.

Its configuration is managed via ALS preferences page.

Configuration

	Source	Data type	Required	Default value
ON/OFF	Preferences: Processing Tab	ON/OFF	∅	OFF
Master dark path	Preferences: Processing Tab	File path	Yes	∅

Control

This process is triggered by the Preprocess pipeline.

Input

Data	Type
image received from the Preprocess pipeline	Image
master dark read from configured path	Image

Behavior

graph LR

START([START])

TEST_ENABLED{{Processing enabled?}}
TEST_SIZE{{Identical dimensions?}}
TEST_TYPE{{Identical data types?}}

CONVERT[Convert master dark]
SUBTRACT[Subtract master dark from image]

RETURN[Return modified image]
UNCHANGED[Return unchanged image]

END([END])

START --> TEST_ENABLED

TEST_ENABLED ----->|No| UNCHANGED
TEST_ENABLED -->|Yes| TEST_SIZE

TEST_SIZE ----->|No| UNCHANGED
TEST_SIZE -->|Yes| TEST_TYPE

TEST_TYPE -->|No| CONVERT
TEST_TYPE -->|Yes| SUBTRACT

CONVERT --> SUBTRACT
SUBTRACT --> RETURN

RETURN --> END
UNCHANGED --> END

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class TEST_ENABLED,TEST_SIZE,TEST_TYPE test
class START,END bounds
class RETURN,UNCHANGED,CONVERT,SUBTRACT step

The master dark is subtracted from the image.

Debayering

Thu, 11 Jun 2026 00:33:38 +0000

Overview

The Debayer process is used on color images in FITS or Raw format.

It generates a color image from the raw image and the description of the Bayer pattern installed on the sensor that generated the image.

Its configuration is managed via ALS preferences page.

Configuration

	Source	Data Type	Required	Default Value
Bayer pattern	Preferences: Processing Tab	choice: - AUTO - GRBG - RGGB - GBRG - BGGR	YES	AUTO

Control

This process is triggered by the Preprocess module.

Stacker

Thu, 11 Jun 2026 00:33:39 +0000

Overview

The Stacker module handles the alignment and stacking of calibrated subs.

Configuration

	Source	Data type	Required	Default value
Alignment ON/OFF	Interface: Stacking controls	ON/OFF	∅	ON
Stacking mode	Interface: Stacking controls	choices: - mean - sum	YES	mean
Detection threshold	Interface: Stacking controls	integer	YES	25

Control

The Stack module is launched in the background at ALS startup

Source	Type	Response
sub(s) in queue	Event	trigger processing

Input

Data	Type
sub at queue front	Image
session alignment reference	Image

Behavior

flowchart LR
Start([START])
FirstSub{{First sub of the session?}}
SetAlignReference[Set sub as alignment reference]
CheckShape{{Sub same dimensions as previous result?}}
CheckAlign{{Alignment ON?}}
AlignImage[Align sub]
StackImage[Add sub to Stack]
ComputeStacking[Compute stacking]
PublishReference[Return alignment reference]
PublishResult[Return generated image]
End([END])

Start --> FirstSub
FirstSub -- YES --> SetAlignReference
SetAlignReference --> PublishReference
FirstSub -- NO --> CheckShape
CheckShape -- YES --> CheckAlign
CheckAlign -- YES --> AlignImage
AlignImage --> StackImage
CheckAlign -- NO --> StackImage
StackImage --> ComputeStacking
ComputeStacking --> PublishResult
CheckShape -- NO --> End
PublishReference --> End
PublishResult --> End

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class Start,End bounds
class SetAlignReference,AlignImage,StackImage,PublishResult,ComputeStacking,PublishReference step
class CheckShape,CheckAlign,FirstSub test

Alignment

If alignment is ON

Process

Thu, 11 Jun 2026 00:33:39 +0000

Overview

The Process pipeline handles visual processing tasks applied to the stacking results.

Configuration

The Process pipeline itself requires no configuration.

The configuration of the visual processing tasks is managed by the processes themselves. See the Behavior section below.

Control

The Process module is launched in the background at ALS startup.

Source	Type	Response
sub(s) in queue	Event	trigger processing

Input

Data	Type
sub at queue front	Image

Behavior

Performs visual processing tasks on the stacking result:

Auto-Stretch

Thu, 11 Jun 2026 00:33:39 +0000

Overview

The Auto-Stretch process optimizes the intensity levels of stacked images, making them visually usable without manual adjustments.

This process is handled by the Process pipeline module.

Configuration

Adjustments can be made through the Processing Panel, located on the right-hand side of the ALS interface.

Control	Type	Action
`Active`	checkbox	Enable or disable the process
`Strength`	slider	Adjust stretch intensity

Refer to the Processing Panel documentation for detailed instructions

Control

The Auto-Stretch process is managed by the Process pipeline

Levels

Thu, 11 Jun 2026 00:33:39 +0000

Overview

The Levels process adjusts the brightness distribution of a stacked image by setting black and white points and tuning midtones.
It allows precise control over image contrast and luminosity, complementing the Auto-Stretch process.

This process is handled by the Process pipeline module.

Configuration

The Levels process parameters are available in the Processing Panel, located on the right-hand side of the ALS interface.

Refer to the Processing Panel documentation for detailed instructions.

RGB Balance

Thu, 11 Jun 2026 00:33:39 +0000

Overview

The RGB Balance process adjusts the relative intensity of the three primary colors — red, green, and blue — to correct or refine the overall color tone of a stacked image.
It allows fine control of image chromatic balance, complementing the Levels and Auto-Stretch processes.

This process is handled by the Process pipeline module.

ℹ️ The RGB Balance process is only available when working with color images.

Configuration

The RGB Balance parameters are available in the Processing Panel, located on the right-hand side of the ALS interface.

Save

Wed, 10 Jun 2026 23:25:49 +0000

Overview

The Save module handles the saving on disk of all images generated by ALS.

Its configuration is managed via ALS preferences

Configuration

	Source	Data type	Required	Default value
work folder	Prefs: Output Tab	path to a folder	Yes	∅
web folder	Prefs: Output Tab	path to a folder	Yes	= work folder
file format	Prefs: Output Tab	choices: - TIFF - PNG - JPEG	Yes	JPEG

Control

The Save module is launched in the background at ALS startup

Server

Thu, 11 Jun 2026 00:20:09 +0000

Overview

The Server utility module exposes ALS processing results through a lightweight HTTP and WebSocket service.

It is responsible for:

Publishing the latest processed stacking result and session metrics in the configured web folder
Serving the viewer web application (index.html, JavaScript and icons)
Streaming live new-image notifications to connected browsers over WebSockets
Providing a QR-code friendly URL so that tablets or phones can join the session quickly

The module runs in its own asyncio event loop and accepts concurrent browser clients. It never alters the processing pipeline; it only serves the web image written by the Save module.

Reference documentation

Thu, 11 Jun 2026 00:33:38 +0000

Overview

This section contains detailed documentation about ALS bits and bolts

🧠 It elaborates on the concepts introduced at the beginning of the user guide

Modules and Processes

Thu, 11 Jun 2026 00:33:38 +0000

Overview

In here, you will find detailed documentation about ALS modules and processes.

From what a module is to how a process works, you will find everything you need to know about the bits and bolts of ALS.

Modules

An ALS module is an elaborated processing unit responsible for a specific task.

It has its own engine
It can be started and stopped at will
It has access to the settings defined in ALS preferences
Its behavior can be controlled through the ALS interface

Modules are dumb and isolated. They have no knowledge of other parts of the application. They just do their job and report to the application

Scanner

Thu, 11 Jun 2026 00:33:38 +0000

Overview

The Scanner module is the entry point for your subs in ALS.

It is responsible for:

Monitoring the appearance of subs in the scan folder
Loading the detected subs

ℹ️ Existing files are ignored

Files present in the scan folder before the Scanner module is started are not detected

ℹ️ Detection of subs is recursive

Subs are detected regardless of the level of subfolders where they appear within the scan folder

Preprocess

Thu, 11 Jun 2026 00:33:38 +0000

Overview

The Preprocess pipeline handles calibration processes

Configuration

The Preprocess pipeline itself requires no configuration.

The configuration of the calibration processes is managed by the processes themselves. See the Behavior section below.

Control

The Preprocess module is launched in the background at ALS startup

Source	Type	Response
sub(s) in queue	Event	trigger calibration

Input

Data	Type
sub at queue front	Image

Behavior

Performs calibration processes on the sub:

Output

Calibrated sub is broadcast

Hot Pixel Removal

Thu, 11 Jun 2026 00:33:38 +0000

Overview

The HotPixelRemove process removes hot pixels from the image.

Its configuration is managed via ALS preferences.

Configuration

	Source	Data Type	Required	Default
ON/OFF	Preferences: Processing Tab	ON/OFF	∅	OFF

Control

This process is controlled by the Preprocess pipeline.

Input

Data	Type
image provided by the Preprocess pipeline	Image

Behavior

graph LR

START([START])

TEST_ENABLED{{Process enabled?}}
TEST_COLOR{{Color image?}}

COMPUTE[Compute average value of neighbors of each pixel]
REPLACE[Replace hot pixel value with the average of its neighbors]

RETURN[Return modified image]
UNCHANGED[Return unchanged image]

END([END])

START --> TEST_ENABLED
TEST_ENABLED -->|Yes| TEST_COLOR
TEST_COLOR ---->|Yes| UNCHANGED
TEST_ENABLED ---->|No| UNCHANGED
TEST_COLOR -->|No| COMPUTE
COMPUTE --> REPLACE
REPLACE --> RETURN
RETURN --> END
UNCHANGED --> END

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class START bounds
class TEST_ENABLED test
class TEST_COLOR test
class COMPUTE step
class UNCHANGED step
class REPLACE step
class RETURN step
class END bounds

Each pixel in the image whose value deviates too much from its neighbors is considered a hot pixel.

Dark Subtraction

Thu, 11 Jun 2026 00:33:38 +0000

Overview

The DarkRemove process subtracts the thermal noise from the image using a user-provided master dark.

Its configuration is managed via ALS preferences page.

Configuration

	Source	Data type	Required	Default value
ON/OFF	Preferences: Processing Tab	ON/OFF	∅	OFF
Master dark path	Preferences: Processing Tab	File path	Yes	∅

Control

This process is triggered by the Preprocess pipeline.

Input

Data	Type
image received from the Preprocess pipeline	Image
master dark read from configured path	Image

Behavior

graph LR

START([START])

TEST_ENABLED{{Processing enabled?}}
TEST_SIZE{{Identical dimensions?}}
TEST_TYPE{{Identical data types?}}

CONVERT[Convert master dark]
SUBTRACT[Subtract master dark from image]

RETURN[Return modified image]
UNCHANGED[Return unchanged image]

END([END])

START --> TEST_ENABLED

TEST_ENABLED ----->|No| UNCHANGED
TEST_ENABLED -->|Yes| TEST_SIZE

TEST_SIZE ----->|No| UNCHANGED
TEST_SIZE -->|Yes| TEST_TYPE

TEST_TYPE -->|No| CONVERT
TEST_TYPE -->|Yes| SUBTRACT

CONVERT --> SUBTRACT
SUBTRACT --> RETURN

RETURN --> END
UNCHANGED --> END

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class TEST_ENABLED,TEST_SIZE,TEST_TYPE test
class START,END bounds
class RETURN,UNCHANGED,CONVERT,SUBTRACT step

The master dark is subtracted from the image.

Debayering

Thu, 11 Jun 2026 00:33:38 +0000

Overview

The Debayer process is used on color images in FITS or Raw format.

It generates a color image from the raw image and the description of the Bayer pattern installed on the sensor that generated the image.

Its configuration is managed via ALS preferences page.

Configuration

	Source	Data Type	Required	Default Value
Bayer pattern	Preferences: Processing Tab	choice: - AUTO - GRBG - RGGB - GBRG - BGGR	YES	AUTO

Control

This process is triggered by the Preprocess module.

Stacker

Thu, 11 Jun 2026 00:33:38 +0000

Overview

The Stacker module handles the alignment and stacking of calibrated subs.

Configuration

	Source	Data type	Required	Default value
Alignment ON/OFF	Interface: Stacking controls	ON/OFF	∅	ON
Stacking mode	Interface: Stacking controls	choices: - mean - sum	YES	mean
Detection threshold	Interface: Stacking controls	integer	YES	25

Control

The Stack module is launched in the background at ALS startup

Source	Type	Response
sub(s) in queue	Event	trigger processing

Input

Data	Type
sub at queue front	Image
session alignment reference	Image

Behavior

flowchart LR
Start([START])
FirstSub{{First sub of the session?}}
SetAlignReference[Set sub as alignment reference]
CheckShape{{Sub same dimensions as previous result?}}
CheckAlign{{Alignment ON?}}
AlignImage[Align sub]
StackImage[Add sub to Stack]
ComputeStacking[Compute stacking]
PublishReference[Return alignment reference]
PublishResult[Return generated image]
End([END])

Start --> FirstSub
FirstSub -- YES --> SetAlignReference
SetAlignReference --> PublishReference
FirstSub -- NO --> CheckShape
CheckShape -- YES --> CheckAlign
CheckAlign -- YES --> AlignImage
AlignImage --> StackImage
CheckAlign -- NO --> StackImage
StackImage --> ComputeStacking
ComputeStacking --> PublishResult
CheckShape -- NO --> End
PublishReference --> End
PublishResult --> End

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class Start,End bounds
class SetAlignReference,AlignImage,StackImage,PublishResult,ComputeStacking,PublishReference step
class CheckShape,CheckAlign,FirstSub test

Alignment

If alignment is ON

Process

Thu, 11 Jun 2026 00:33:38 +0000

Overview

The Process pipeline handles visual processing tasks applied to the stacking results.

Configuration

The Process pipeline itself requires no configuration.

The configuration of the visual processing tasks is managed by the processes themselves. See the Behavior section below.

Control

The Process module is launched in the background at ALS startup.

Source	Type	Response
sub(s) in queue	Event	trigger processing

Input

Data	Type
sub at queue front	Image

Behavior

Performs visual processing tasks on the stacking result:

Auto-Stretch

Thu, 11 Jun 2026 00:33:38 +0000

Overview

The Auto-Stretch process optimizes the intensity levels of stacked images, making them visually usable without manual adjustments.

This process is handled by the Process pipeline module.

Configuration

Adjustments can be made through the Processing Panel, located on the right-hand side of the ALS interface.

Control	Type	Action
`Active`	checkbox	Enable or disable the process
`Strength`	slider	Adjust stretch intensity

Refer to the Processing Panel documentation for detailed instructions

Control

The Auto-Stretch process is managed by the Process pipeline

Levels

Thu, 11 Jun 2026 00:33:38 +0000

Overview

This process is handled by the Process pipeline module.

Configuration

The Levels process parameters are available in the Processing Panel, located on the right-hand side of the ALS interface.

Refer to the Processing Panel documentation for detailed instructions.

RGB Balance

Thu, 11 Jun 2026 00:33:38 +0000

Overview

This process is handled by the Process pipeline module.

ℹ️ The RGB Balance process is only available when working with color images.

Configuration

The RGB Balance parameters are available in the Processing Panel, located on the right-hand side of the ALS interface.

Save

Wed, 10 Jun 2026 23:25:49 +0000

Overview

The Save module handles the saving on disk of all images generated by ALS.

Its configuration is managed via ALS preferences

Configuration

	Source	Data type	Required	Default value
work folder	Prefs: Output Tab	path to a folder	Yes	∅
web folder	Prefs: Output Tab	path to a folder	Yes	= work folder
file format	Prefs: Output Tab	choices: - TIFF - PNG - JPEG	Yes	JPEG

Control

The Save module is launched in the background at ALS startup

Server

Thu, 11 Jun 2026 00:20:09 +0000

Overview

The Server utility module exposes ALS processing results through a lightweight HTTP and WebSocket service.

It is responsible for:

Publishing the latest processed stacking result and session metrics in the configured web folder
Serving the viewer web application (index.html, JavaScript and icons)
Streaming live new-image notifications to connected browsers over WebSockets

The module runs in its own asyncio event loop and accepts concurrent browser clients. It never alters the processing pipeline; it only serves the web image written by the Save module.

Reference documentation

Thu, 11 Jun 2026 00:33:39 +0000

Overview

This section contains detailed documentation about ALS bits and bolts

🧠 It elaborates on the concepts introduced at the beginning of the user guide

Modules and Processes

Thu, 11 Jun 2026 00:33:39 +0000

Overview

In here, you will find detailed documentation about ALS modules and processes.

From what a module is to how a process works, you will find everything you need to know about the bits and bolts of ALS.

Modules

An ALS module is an elaborated processing unit responsible for a specific task.

It has its own engine
It can be started and stopped at will
It has access to the settings defined in ALS preferences
Its behavior can be controlled through the ALS interface

Modules are dumb and isolated. They have no knowledge of other parts of the application. They just do their job and report to the application

Scanner

Thu, 11 Jun 2026 18:38:13 +0000

Overview

The Scanner module is the entry point for your subs in ALS.

It is responsible for:

Monitoring the appearance of subs in the scan folder
Loading the detected subs

ℹ️ Existing files are ignored

Files present in the scan folder before the Scanner module is started are not detected

ℹ️ Detection of subs is recursive

Subs are detected regardless of the level of subfolders where they appear within the scan folder

Preprocess

Thu, 11 Jun 2026 00:33:39 +0000

Overview

The Preprocess pipeline handles calibration processes

Configuration

The Preprocess pipeline itself requires no configuration.

The configuration of the calibration processes is managed by the processes themselves. See the Behavior section below.

Control

The Preprocess module is launched in the background at ALS startup

Source	Type	Response
sub(s) in queue	Event	trigger calibration

Input

Data	Type
sub at queue front	Image

Behavior

Performs calibration processes on the sub:

Output

Calibrated sub is broadcast

Hot Pixel Removal

Thu, 11 Jun 2026 00:33:39 +0000

Overview

The HotPixelRemove process removes hot pixels from the image.

Its configuration is managed via ALS preferences.

Configuration

	Source	Data Type	Required	Default
ON/OFF	Preferences: Processing Tab	ON/OFF	∅	OFF

Control

This process is controlled by the Preprocess pipeline.

Input

Data	Type
image provided by the Preprocess pipeline	Image

Behavior

graph LR

START([START])

TEST_ENABLED{{Process enabled?}}
TEST_COLOR{{Color image?}}

COMPUTE[Compute average value of neighbors of each pixel]
REPLACE[Replace hot pixel value with the average of its neighbors]

RETURN[Return modified image]
UNCHANGED[Return unchanged image]

END([END])

START --> TEST_ENABLED
TEST_ENABLED -->|Yes| TEST_COLOR
TEST_COLOR ---->|Yes| UNCHANGED
TEST_ENABLED ---->|No| UNCHANGED
TEST_COLOR -->|No| COMPUTE
COMPUTE --> REPLACE
REPLACE --> RETURN
RETURN --> END
UNCHANGED --> END

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class START bounds
class TEST_ENABLED test
class TEST_COLOR test
class COMPUTE step
class UNCHANGED step
class REPLACE step
class RETURN step
class END bounds

Each pixel in the image whose value deviates too much from its neighbors is considered a hot pixel.

Dark Subtraction

Thu, 11 Jun 2026 00:33:39 +0000

Overview

The DarkRemove process subtracts the thermal noise from the image using a user-provided master dark.

Its configuration is managed via ALS preferences page.

Configuration

	Source	Data type	Required	Default value
ON/OFF	Preferences: Processing Tab	ON/OFF	∅	OFF
Master dark path	Preferences: Processing Tab	File path	Yes	∅

Control

This process is triggered by the Preprocess pipeline.

Input

Data	Type
image received from the Preprocess pipeline	Image
master dark read from configured path	Image

Behavior

graph LR

START([START])

TEST_ENABLED{{Processing enabled?}}
TEST_SIZE{{Identical dimensions?}}
TEST_TYPE{{Identical data types?}}

CONVERT[Convert master dark]
SUBTRACT[Subtract master dark from image]

RETURN[Return modified image]
UNCHANGED[Return unchanged image]

END([END])

START --> TEST_ENABLED

TEST_ENABLED ----->|No| UNCHANGED
TEST_ENABLED -->|Yes| TEST_SIZE

TEST_SIZE ----->|No| UNCHANGED
TEST_SIZE -->|Yes| TEST_TYPE

TEST_TYPE -->|No| CONVERT
TEST_TYPE -->|Yes| SUBTRACT

CONVERT --> SUBTRACT
SUBTRACT --> RETURN

RETURN --> END
UNCHANGED --> END

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class TEST_ENABLED,TEST_SIZE,TEST_TYPE test
class START,END bounds
class RETURN,UNCHANGED,CONVERT,SUBTRACT step

The master dark is subtracted from the image.

Flat Calibration

Thu, 11 Jun 2026 00:33:39 +0000

Overview

The RemoveFlat process divides each sub by a user-provided master flat to remove optical vignetting, dust motes, and pixel-to-pixel response variations.

Its configuration is managed via the ALS preferences page.

Configuration

	Source	Data type	Required	Default value
ON/OFF	Preferences: Processing Tab	ON/OFF	∅	OFF
Master flat path	Preferences: Processing Tab	File path	Yes	∅

Control

This process is triggered by the Preprocess pipeline.

Input

Data	Type
image received from the Preprocess pipeline	Image
master flat read from configured path	Image

Behavior

graph LR

START([START])

TEST_ENABLED{{Processing enabled?}}
READ_FLAT[Read master flat]
TEST_SHAPE{{Identical dimensions?}}
    NORMALIZE[Normalize by robust scale]
    SAFEGUARD[Apply epsilon floor]
DIVIDE[Divide image by normalized flat]
CLIP[Clip to 16-bit range]
RETURN[Return calibrated image]
UNCHANGED[Return unchanged image]

END([END])

START --> TEST_ENABLED

TEST_ENABLED ----->|No| UNCHANGED
TEST_ENABLED -->|Yes| READ_FLAT

READ_FLAT ----->|Failed| UNCHANGED
READ_FLAT -->|Ok| TEST_SHAPE

TEST_SHAPE ----->|No| UNCHANGED
TEST_SHAPE -->|Yes| NORMALIZE

NORMALIZE --> SAFEGUARD
SAFEGUARD --> DIVIDE
DIVIDE --> CLIP
CLIP --> RETURN

RETURN --> END
UNCHANGED --> END

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classDef step fill: #444, stroke: #622, stroke-width:2px, color: #c6c6c6, font-family: 'Poppins',sans-serif
classDef wait  fill: #444, stroke: #262,stroke-width: 2px, color: #c6c6c6, font-family:'Poppins', sans-serif
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class TEST_ENABLED,TEST_SHAPE test
class START,END bounds
class RETURN,UNCHANGED,READ_FLAT,NORMALIZE,SAFEGUARD,DIVIDE,CLIP step

The master flat is loaded from disk, converted to a normalized float32 calibration frame, and protected with a small epsilon floor before dividing the sub.

Debayering

Thu, 11 Jun 2026 22:56:10 +0000

Overview

The Debayer process is used on color images in FITS or Raw format.

It generates a color image from the raw image and the description of the Bayer pattern installed on the sensor that generated the image.

Its configuration is managed via ALS preferences page.

Configuration

	Source	Data Type	Required	Default Value
Bayer pattern	Preferences: Processing Tab	choice: - AUTO - GRBG - RGGB - GBRG - BGGR	YES	AUTO

Control

This process is triggered by the Preprocess module.

Stacker

Thu, 11 Jun 2026 17:57:08 +0000

Overview

The Stacker module handles the alignment and stacking of calibrated subs.

Configuration

	Source	Data type	Required	Default value
Alignment ON/OFF	Interface: Stacking controls	ON/OFF	∅	ON
Stacking mode	Interface: Stacking controls	choices: - mean - sum	YES	mean
Minimum matches	Interface: Stacking controls	integer	YES	25

Control

The Stack module is launched in the background at ALS startup

Source	Type	Response
sub(s) in queue	Event	trigger processing

Input

Data	Type
sub at queue front	Image
session alignment reference	Image

Behavior

flowchart LR
Start([START])
FirstSub{{First sub of the session?}}
SetAlignReference[Set sub as alignment reference]
CheckShape{{Sub same dimensions as previous result?}}
CheckAlign{{Alignment ON?}}
AlignImage[Align sub]
StackImage[Add sub to Stack]
ComputeStacking[Compute stacking]
PublishReference[Return alignment reference]
PublishResult[Return generated image]
End([END])

Start --> FirstSub
FirstSub -- YES --> SetAlignReference
SetAlignReference --> PublishReference
FirstSub -- NO --> CheckShape
CheckShape -- YES --> CheckAlign
CheckAlign -- YES --> AlignImage
AlignImage --> StackImage
CheckAlign -- NO --> StackImage
StackImage --> ComputeStacking
ComputeStacking --> PublishResult
CheckShape -- NO --> End
PublishReference --> End
PublishResult --> End

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class Start,End bounds
class SetAlignReference,AlignImage,StackImage,PublishResult,ComputeStacking,PublishReference step
class CheckShape,CheckAlign,FirstSub test

Alignment

If alignment is ON

Process

Thu, 11 Jun 2026 00:33:39 +0000

Overview

The Process pipeline handles visual processing tasks applied to the stacking results.

Configuration

The Process pipeline itself requires no configuration.

The configuration of the visual processing tasks is managed by the processes themselves. See the Behavior section below.

Control

The Process module is launched in the background at ALS startup.

Source	Type	Response
sub(s) in queue	Event	trigger processing

Input

Data	Type
sub at queue front	Image

Behavior

Performs visual processing tasks on the stacking result:

Auto-Stretch

Thu, 11 Jun 2026 00:33:39 +0000

Overview

The Auto-Stretch process optimizes the intensity levels of stacked images, making them visually usable without manual adjustments.

This process is handled by the Process pipeline module.

Configuration

Adjustments can be made through the Processing Panel, located on the right-hand side of the ALS interface.

Control	Type	Action
`Active`	checkbox	Enable or disable the process
`Strength`	slider	Adjust stretch intensity

Refer to the Processing Panel documentation for detailed instructions

Control

The Auto-Stretch process is managed by the Process pipeline

Levels

Thu, 11 Jun 2026 00:33:39 +0000

Overview

This process is handled by the Process pipeline module.

Configuration

The Levels process parameters are available in the Processing Panel, located on the right-hand side of the ALS interface.

Refer to the Processing Panel documentation for detailed instructions.

RGB Balance

Thu, 11 Jun 2026 00:33:39 +0000

Overview

The RGB Balance process adjusts the relative intensity of the three primary colors — red, green, and blue — to correct or refine the overall color tone of a stacked image. It also controls global color saturation, letting you reinforce or tame chroma while keeping exposure unchanged. These parameters allow fine control of image chromatic balance, complementing the Levels and Auto-Stretch processes.

This process is handled by the Process pipeline module.

Save

Wed, 10 Jun 2026 23:25:50 +0000

Overview

The Save module handles the saving on disk of all images generated by ALS.

Its configuration is managed via ALS preferences

Configuration

	Source	Data type	Required	Default value
work folder	Prefs: Output Tab	path to a folder	Yes	∅
web folder	Prefs: Output Tab	path to a folder	Yes	= work folder
file format	Prefs: Output Tab	choices: - TIFF - PNG - JPEG	Yes	JPEG

Control

The Save module is launched in the background at ALS startup

Server

Thu, 11 Jun 2026 00:20:09 +0000

Overview

The Server utility module exposes ALS processing results through a lightweight HTTP and WebSocket service.

It is responsible for:

Publishing the latest processed stacking result and session metrics in the configured web folder
Serving the viewer web application (index.html, JavaScript and icons)
Streaming live new-image notifications to connected browsers over WebSockets
Providing a QR-code friendly URL so that tablets or phones can join the session quickly

The module runs in its own asyncio event loop and accepts concurrent browser clients. It never alters the processing pipeline; it only serves the web image written by the Save module.