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Master PixInsight's Astrophotography Statistics: Analyze, Adjust, Enhance.

Susie M

Thursday, November 02, 2023

Welcome to the cosmos of PixInsight and its invaluable tool, the Statistics Dialog.

In the realm of Astrophotography, understanding the intricacies of your images is akin to deciphering the mysteries of the universe. This introduction is your launchpad into a world where numbers and statistics transform ordinary images into extraordinary cosmic wonders.

The PixInsight Statistics Dialog is not just any statistical tool; it's the key to unlocking the potential of your Astrophotography. It provides you with a comprehensive set of statistical measurements, from the minimum and maximum values to the mean, median, and standard deviation. These statistics go beyond mere numbers; they reveal the essence of your images, shedding light on their quality, clarity, and potential.

Why is understanding these statistical properties crucial? Because in the world of Astrophotography, your images are your canvas, and statistics are your brushes. They allow you to assess image quality, identify potential issues, and make informed decisions during the image enhancement and analysis process. In short, they are your gateway to capturing the beauty of the cosmos in all its glory.

It empowers you to unveil the hidden details in your celestial images, from the majestic galaxies to the delicate nebulae and star clusters. Whether you're a novice Astrophotographer or a seasoned stargazer, the Statistics Dialog is a tool that can elevate your work to new heights.

PixInsight | Statistics Dialog | Kozmosi.io

In the upcoming sections, we will guide you through the essential aspects of PixInsight's Statistics Dialog. We'll explore its role in assessing image quality, its seamless integration into image processing workflows, and its ability to analyze specific regions of interest. Real-time preview windows will become your virtual portal to the cosmos, and you'll learn how to fine-tune your images with precision.

We'll delve into the various display options for statistics, ensuring you understand how to tailor your data visualization to your unique needs. Finally, we'll take a comprehensive tour of the statistics, uncovering the wealth of insights they offer for your Astrophotography projects.

Join us as we unveil the magic of statistics in Astrophotography and watch your images reach new dimensions of clarity and beauty. Let's begin this extraordinary voyage together.

Assessing Image Quality

Understanding the quality of your images is paramount in the world of Astrophotography. PixInsight's Statistics Dialog equips you with the tools you need to assess image quality with precision. By analyzing statistical properties such as mean, median, and standard deviation, you gain insights into potential issues that might be affecting the clarity of your Astrophotographs. Unveiling these hidden imperfections is the first step towards producing stunning images that captivate your audience.

Mean and Standard Deviation:

Statistics like mean and standard deviation provide insights into the overall brightness and contrast of your image. A high mean value may indicate overexposure, while a high standard deviation could suggest excessive noise. By understanding these statistics, you can immediately identify issues that may require correction.

Median and Variance:

Median represents the middle value in your data, which can be crucial for revealing the central tendency of your image's pixel values. Variance quantifies the spread of pixel values. A high variance might signal that your image has a broad range of brightness levels, which could affect the clarity of your Astrophotograph.

Extreme Values:

The minimum and maximum values are your windows to the darkest and brightest parts of your image. If these values are too close to the image's limits (0 and 1), you risk losing critical details in your photograph. Understanding these extreme values helps ensure that your image's dynamic range is well-preserved.

By delving into these statistical properties, you can quickly assess image quality and pinpoint potential issues in your Astrophotograph. This information is invaluable, as it empowers you to make informed decisions about how to enhance your image effectively. You might decide to adjust exposure settings, apply noise reduction techniques, or modify the stretching parameters to bring out the desired details in your Astrophotograph.

Analyzing Specific Regions

Astrophotography isn't just about the grandeur of the cosmos; it's also about the intricate details. PixInsight's Statistics Dialog allows you to zoom in and analyze specific regions of interest within your images. Compare statistical properties between different areas, revealing nuances that might be overlooked at first glance. This level of precision helps you achieve remarkable clarity in your Astrophotography.

However, understanding how to use PixInsight's preview windows is the key to isolating and scrutinizing these specific areas effectively. These preview windows act as your portal to in-depth analysis, and here's how you can make the most of them:

Creating a Preview Window:

Start by creating a preview window for your image. This is done by selecting a specific area of interest that you wish to analyze more closely. The preview window allows you to isolate that region while keeping an eye on the entire image.

Accessing the Statistics Dialog:

With the preview window in place, open the Statistics Dialog, either through the process menu or by using the search bar. The key advantage here is that the statistics you'll obtain are specific to the area covered by the preview window.

In-Depth Analysis:

Now, you can delve into the statistics of this localized region. Explore properties like mean, median, and standard deviation for this specific area, gaining insights that might be concealed when analyzing the entire image as a whole.

Comparing Regions:

PixInsight allows you to create multiple preview windows, each covering a different region of interest. This capability is invaluable when you want to compare statistical properties between different areas within your image. For instance, you can compare the clarity of the central region of a galaxy to its outer regions or assess the noise levels in various parts of a nebula.

Real-Time Statistics:

As you switch between these preview windows, the Statistics Dialog updates in real-time. This feature ensures that you can instantly observe the impact of any adjustments you make to the specific area you're analyzing. It's a dynamic way to fine-tune your image without affecting the entire photograph.

PixInsight | Statistics Dialog | Kozmosi.io

Creation of a Preview Window

PixInsight | Statistics Dialog | Kozmosi.io

Preview Window Selected

The PixInsight preview windows, combined with the Statistics Dialog, give you the power to scrutinize the nuances of your Astrophotographs. It's like having a microscope for your celestial canvas, allowing you to uncover the details that make your images truly captivating.

For those new to Preview Windows in PixInsight, you can refer to the relevant chapter in the A to Z of PixInsight Masterclass for a detailed explanation. These preview windows are your virtual view clients, and they play a pivotal role in your quest for the perfect Astrophotograph.

Real-Time Preview Windows

In the world of PixInsight, the term "preview windows" may sound familiar, but it's essential to distinguish real-time preview windows from the preview windows mentioned in the previous section.

Real-time preview windows offer dynamic feedback, allowing you to observe the impact of your adjustments without altering your original image. In contrast, static preview windows are used to isolate specific regions for analysis but do not update in real-time.

As you fine-tune parameters in tools like the Curve Transformation Tool, the Statistics Dialog updates in real-time, offering you immediate feedback. This dynamic approach ensures that you achieve your desired results with precision and efficiency.

PixInsight | Statistics Dialog | Kozmosi.io

Real-Time preview of Curve Transformation and Statistics

Statistics Display Options

In the realm of Astrophotography, precision is key. To achieve this, it's not just about gathering statistical data; it's also about how you present and interpret that data. PixInsight's Statistics Dialog offers a range of display options for statistics, allowing you to tailor the representation of your data to your specific needs. Let's explore the differences between scientific notation, normalized, and clipped display options:

Scientific Notation:

Precision in Numbers: Scientific notation is a display option that showcases statistical values in a precise and concise format. It is particularly useful when dealing with a wide range of values, such as pixel brightness or standard deviation.

Exponential Form: In scientific notation, numbers are expressed as a coefficient and an exponent. For instance, instead of displaying a very small value as "0.00000123," scientific notation represents it as "1.23 x 10^-6." This form helps you understand the magnitude of values more easily.

Effective with Extremes: When working with Astrophotographic data that can span several orders of magnitude, such as brightness levels or pixel values, scientific notation ensures that you can clearly differentiate between them without being overwhelmed by a string of zeros.

Normalized Display:

Consistency in Scaling: Normalized display is designed to maintain consistency in the scaling of statistics. It ensures that the scale estimates are consistent with the standard deviation of a normal distribution.

Multiplication with Constants: Normalized values are obtained by multiplying statistical measurements with specific constants. For example, the average deviation is multiplied by 1.2533, the MAD by 1.4826, and so on. This scaling provides you with a consistent reference point for comparison.

Understanding Relative Values: Normalized display allows you to understand how each statistic relates to the standard deviation of a normal distribution, offering a common baseline for evaluating different statistics.

Clipped Display:

Focusing on Critical Ranges: Clipped display is particularly useful when you want to focus on specific critical ranges within your data. It computes statistics only for the subset of pixel sample values within the (0, 1) normalized range, excluding pure black and white pixels.

Avoiding Useless Information: Enabling the "Unclipped" option in PixInsight's Statistics Tool recalculates statistics for the unclipped (0, 1) range. This can be especially valuable when your image contains a substantial amount of black and/or white pixels, and computing statistics for the full range would result in mostly useless data.

Enhanced Clarity: By using clipped display, you can concentrate on the parts of your image that matter most. This display option prevents irrelevant data from skewing your analysis and ensures that you're focusing on the information that contributes to image quality.

PixInsight | Statistics Panel | Kozmosi.io

Statistics Dialog Normalization Constants

Understanding these display options allows you to interpret your Astrophotographic data more effectively. Whether you prefer the precision of scientific notation, the consistency of normalized values, or the focus of clipped display, PixInsight's Statistics Dialog empowers you to customize the representation of your statistics to match your unique needs.

Statistics Explained

PixInsight's Statistics Dialog offers a treasure trove of statistical insights, it is where you discover the wealth of data that can elevate your Astrophotography to new heights. Here, we'll delve into each of the available statistics, shedding light on what they represent and how they contribute to your image analysis, but keep in mind that selecting too many statistics can increase computation time.


Description: Count represents the number of pixel samples used to compute statistics for each channel. It's shown both as a pixel count and as a percentage of the total pixels in the image.

Significance: Count provides a fundamental understanding of the sample size, offering insights into the data's significance. A higher count typically indicates a larger dataset for statistical analysis.

PixInsight | Statistics Panel | Count | Kozmosi.io


Description: The mean is the arithmetic average of the pixel values in your image.

Significance: Mean serves as a key indicator of the overall brightness or intensity of your image. A high mean suggests a bright image, while a low mean indicates a darker one.

PixInsight | Statistics Panel | Mean | Kozmosi.io


Description: Modulus represents the sum of the absolute sample values.

Significance: Modulus helps you understand the overall magnitude of the pixel values, irrespective of their sign. It can be particularly useful for quantifying the overall intensity of an image.

PixInsight | Statistics Panel | Modulus | Kozmosi.io


Description: Norm is the sum of sample values, which, for normal images, is equivalent to the modulus. However, in cases where pixel samples can be negative, the norm can differ from the modulus.

Significance: Norm is useful for measuring the sum of pixel values, considering both positive and negative values. It provides a more comprehensive view of the image's intensity.

PixInsight | Statistics Panel | Norm | Kozmosi.io

Sum of Squares:

Description: The sum of squares represents the sum of the squares of all sample values.

Significance: Sum of squares quantifies the overall magnitude of pixel values while emphasizing their squared relationship. It's valuable for understanding the distribution of pixel intensities.

PixInsight | Statistics Panel | Sum of Squares | Kozmosi.io

Mean of Squares:

Description: The mean of squares calculates the average of the squares of all sample values.

Significance: Mean of squares extends the concept of the sum of squares, offering insights into the average squared intensity of the image.

PixInsight | Statistics Panel | Mean of Squares.io


Description: Median represents the middle value in your data when arranged in ascending order.

Significance: Median serves as a robust measure of central tendency and is particularly valuable when dealing with data that may contain outliers or extreme values.

PixInsight | Statistics Panel | Median | Kozmosi.io


Description: Variance quantifies the spread or dispersion of pixel values from the mean.

Significance: Variance helps you understand the degree of variation in pixel intensities. A high variance indicates a wider range of brightness levels in the image.

PixInsight | Statistics Panel | Variance | Kozmosi.io

Standard Deviation:

Description: Standard deviation measures the average deviation of pixel values from the mean.

Significance: Standard deviation provides a precise estimate of how much individual pixel values deviate from the mean, offering insights into the image's contrast and noise levels.

PixInsight | Statistics Panel | Standard Deviation | Kozmosi.io

Average Absolute Deviation:

Description: Average absolute deviation calculates the average of the absolute deviations of pixel values from the median.

Significance: Average absolute deviation is a robust measure of data spread, focusing on the average absolute differences from the central tendency.

PixInsight | Statistics Panel | Average Absolute Deviation: | Kozmosi.io

Median Absolute Deviation (MAD):

Description: Median Absolute Deviation computes the median of the absolute deviations of pixel values from the median.

Significance: MAD is a robust measure of data variability, emphasizing the median's influence on the analysis. It's less sensitive to outliers than some other measures.

PixInsight | Statistics Panel | Median Absolute Deviation (MAD): | Kozmosi.io

Square Root of Biweight Midvariance:

Description: The square root of biweight midvariance is a statistical measure used to assess the midvariance of pixel values.

Significance: This statistic quantifies the midvariance while considering the influence of extreme values. It's especially valuable when dealing with data that may have outliers.

PixInsight | Statistics Panel | Square Root of Biweight Midvariance: | Kozmosi.io

Square Root of Percentage Bend Midvariance:

Description: The square root of percentage bend midvariance assesses the midvariance of pixel values while considering the percentage of bending performed.

Significance: This statistic combines midvariance assessment with a percentage bending factor, offering insights into data distribution and concentration.

PixInsight | Statistics Panel | Square Root of Percentage Bend Midvariance: | Kozmosi.io

Sn and Qn Scale Estimators:

Description: Sn and Qn are scale estimators designed to assess the distribution and variability of pixel values.

Significance: These estimators provide robust assessments of data scale, making them valuable in scenarios where data may have outliers or non-normal distributions.

PixInsight | Statistics Panel | Sn and Qn Scale Estimators: | Kozmosi.io

Minimum and Maximum:

Description: Minimum and maximum represent the extreme sample values in your data.

Significance: Minimum and maximum help you identify the darkest and brightest parts of your image. They are critical for assessing the dynamic range of your data.

PixInsight | Statistics Panel | Minimum and Maximum: | Kozmosi.io

Positions of Extreme Values:

Description: Positions of extreme values reveal the coordinates (in image coordinates) of the first occurrences of the extreme sample values (minimum and maximum).

Significance: This statistic provides you with spatial information about the locations of the darkest and brightest areas in your image, helping you pinpoint specific regions of interest.

PixInsight | Statistics Panel | Positions of Extreme Values: | Kozmosi.io

Each of these statistics plays a distinct role in analyzing and understanding the properties of your Astrophotographic data. Whether you're assessing image quality, evaluating processing steps, or making informed decisions during enhancement and analysis, these statistics empower you with the knowledge needed to bring out the beauty of the cosmos in your images.


Using the wrench icon in the top left of the Statistics Dialog Panel you can configure which statistics to display, as mentioned earlier these statistics are calculated for each view and some cannot be cached. Be especially careful with the Sn and Qn Statistics as they are computationally expensive.

PixInsight | Statistics Panel | Settings | Kozmosi.io


PixInsight's Statistics Dialog isn't just a tool; it's your secret weapon for elevating your Astrophotography game. Understanding the statistical properties of your images can mean the difference between ordinary and extraordinary results. By assessing image quality, seamlessly integrating statistics into your workflow, and analyzing specific regions, you can take your Astrophotography to new heights.

The real-time preview windows provide you with the power of instant feedback, ensuring you achieve your desired results with precision. Meanwhile, the flexible display options for statistics allow you to tailor your data visualization to your preferences.

As you dive into the statistics, you'll unlock a treasure trove of insights that guide your image enhancement and analysis. Remember that the key to mastering this tool lies in selecting the statistics that matter most to your unique projects.

With PixInsight's Statistics Dialog, you're not just processing images; you're embarking on a journey to reveal the wonders of the cosmos. So, embrace the power of statistics, harness their potential, and let your Astrophotography shine like never before.

Stay tuned for more Astrophotography insights, and don't forget to explore PixInsight's Statistics Dialog to unlock the secrets of your celestial images.

At Kozmosi.io, we're committed to guiding you on this celestial journey, offering insights, techniques, and a platform where the universe's wonders come alive. Join us, and let's explore the cosmos together. Just Imagine, What's Out There. Remember, the possibilities are endless when it comes to capturing the beauty of the cosmos.

We're not just a platform, we're your cosmic compass, illuminating the intricate pathways of image processing. Dive deep into our courses, and you'll find a universe of knowledge waiting to be explored.

From the basics to the advanced, every chapter is a step closer to mastering the A to Z of PixInsight. So, if you've ever dreamt of painting your own celestial masterpieces, now's the time. Join us at Kozmosi, and let's chart this stellar journey together.

References and Additional Resources

Many of the concepts in this article were inspired by the following resources and I would highly recommend you check them out!
1. https://pixinsight.com/doc/tools/ImageIntegration/ImageIntegration.html

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Statistics Dialog | PixInsight | Kozmosi.io