How to Stack Sun Video with Sigma-Clip Stacking
Process solar videos safely online. Stack white light and H-alpha footage to reveal sunspots, granulation, and prominences.
Advanced Mode Tutorial
This guide covers manual configuration in Advanced Mode where you select the stacking algorithm and fine-tune all parameters. For automatic processing, try Quick Mode - it detects your video type and applies optimal settings automatically.
TL;DR
Want full control over your Sun processing? Sigma-Clip Stacking is a Intermediate-level algorithm. Statistical outlier rejection - for scientific-quality results It works especially well for Sunspots with umbra/penumbra structure. This guide shows you how to configure Sigma-Clip Stacking in Advanced Mode for optimal results.
Introduction
Sun is one of the most rewarding targets for amateur astrophotographers. With its Sunspots with umbra/penumbra structure and Solar granulation (convection cells), even modest equipment can capture impressive detail. However, raw video footage straight from your camera rarely shows the full potential of your observations.
This is where Sigma-Clip Stacking comes in. By intelligently combining hundreds or thousands of video frames, Sigma-Clip Stacking Calculates mean and standard deviation for each pixel across all frames. The result? A single image with dramatically improved detail and reduced noise.
In this guide, you'll learn exactly how to use Sigma-Clip Stacking to process your Sun videos using Uranum AstroStack AI - a cloud-based tool that replaces complex desktop software like PIPP, AutoStakkert, and Registax with a simple, browser-based workflow.
Whether you're using a smartphone through an eyepiece or a dedicated planetary camera, this tutorial will help you achieve professional-quality results.
What is Sigma-Clip Stacking?
Uses statistics to find and reject unusual pixel values (outliers beyond a sigma threshold), then averages the remaining "normal" pixels. Excellent for removing random artifacts like cosmic rays while preserving real detail.
How It Works:
- 1Calculates mean and standard deviation for each pixel across all frames
- 2Values beyond 2.5 sigma (standard deviations) are flagged as outliers
- 3Iterates 3 times to catch outliers that skewed initial statistics
- 4Final image averages only the "normal" values
Best For:
- Removing cosmic ray hits that appear as bright dots
- Cleaning hot pixels and column defects from uncooled sensors
- Videos contaminated with multiple satellite trails
- Scientific imaging where data integrity matters
Not Recommended For:
- •Very noisy footage where signal looks like noise to the algorithm
- •Low frame count (<300) - statistics become unreliable
- •When you want to preserve rare sharp details (they may be clipped)
Why Use Sigma-Clip Stacking for Sun?
Sun presents unique challenges for astrophotographers: CRITICAL SAFETY: Must use certified solar filter or projection and Daytime seeing is typically worse than nighttime. Sigma-Clip Stacking is one of the recommended algorithms for Sun because it effectively addresses these challenges.
Sigma-Clip Stacking is Recommended for Sun
- Feature Enhancement: Sun's Sunspots with umbra/penumbra structure benefit from Sigma-Clip Stacking's ability to Removing cosmic ray hits that appear as bright dots.
- Challenge Mitigation: The CRITICAL SAFETY: Must use certified solar filter or projection is handled well because Sigma-Clip Stacking Values beyond 2.5 sigma (standard deviations) are flagged as outliers.
- Skill Level: As a Intermediate-level algorithm, Sigma-Clip Stacking is suited for users who want more control over results.
Pro tip: For Sun, you might also try Median Stacking or Weighted Quality Stacking for comparison.
Step-by-Step Tutorial
Follow these steps to process your Sun video using Uranum AstroStack AI. The entire process takes about 5-10 minutes.
Step 1: Capture Your Sun Video
For best results, capture 3,000-10,000 frames at 80-150 fps. Maximum duration: 3-5 minutes (rotation negligible). Use 1-5ms exposure at Low-Medium (120-250) gain.
Tip: SAFETY FIRST: Use Baader solar film, Herschel wedge, or solar telescope only
Step 2: Upload Your Sun Video
Drag and drop your Sun video file into Uranum. We support AVI, SER, MP4, MOV, and MKV formats (up to 1.5GB free, 4GB Starter, 10GB Pro).
Tip: SER format preserves maximum quality. MP4/MOV have compression artifacts but still work well.
Step 3: Select Sun as Object Type
Choose "Sun" from the object type dropdown. This applies optimized defaults including stack percentage (35-45%) for average seeing and enhancement settings tuned for Sunspots with umbra/penumbra structure.
Tip: Quick Mode will auto-detect optimal settings. Use Advanced Mode only if you need specific control.
Step 4: Choose Your Mode
Quick Mode: Automatic processing with intelligent frame selection - recommended for most users. Advanced Mode: Manual control over Sigma-Clip Stacking and all parameters.
Tip: Quick Mode uses knee-detection to find optimal stack percentage automatically.
Step 5: For Advanced Mode: Select Sigma-Clip Stacking
In the Stacking section, choose "Sigma-Clip Stacking". Statistical outlier rejection - for scientific-quality results
Tip: Sigma-Clip Stacking is Intermediate-level. Removing cosmic ray hits that appear as bright dots.
Step 6: Set Stack Percentage Based on Seeing
Adjust based on your seeing conditions: Poor (20-30%), Average (35-45%), Good (50-60%), Excellent (60-75%). When in doubt, start with 35-45%.
Tip: Lower percentage = sharper but noisier. Higher percentage = smoother but potentially softer.
Step 7: Start Processing
Click "Start Processing". Uranum analyzes frames, ranks them by quality, stacks the best ones, and applies enhancements. Processing typically takes 2-5 minutes.
Tip: Track progress in real-time. Processing time depends on frame count and your tier.
Step 8: Download Your Result
Compare before/after using the slider. Download in PNG (8/16-bit), TIFF (16-bit), or FITS (32-bit for scientific use).
Tip: 16-bit TIFF preserves the most data for further processing in PixInsight, Photoshop, etc.
Recommended Settings for Sun + Sigma-Clip Stacking
These are recommended starting values for Sun videos with Sigma-Clip Stacking in Advanced Mode. Use them as a baseline and adjust based on your specific video quality and conditions.
| Setting | Value | Explanation |
|---|---|---|
| Capture Duration | 3-5 minutes (rotation negligible) | Sun has specific rotation limits. Exceeding this causes motion blur that stacking cannot fix. |
| Frame Count Target | 3,000-10,000 frames | More frames = more to choose from. Capture at 80-150 fps for optimal sampling. |
| Stack Percentage (Average Seeing) | 35-45% | For typical seeing conditions, stack 35-45% of frames. Adjust based on your seeing: poor (20-30%), average (35-45%), good (50-60%), excellent (60-75%). Quick Mode auto-detects optimal percentage. |
| Stacking Algorithm | Sigma-Clip Stacking | Statistical outlier rejection - for scientific-quality results |
| Wavelet Preset | Subtle | Sun benefits from subtle sharpening (solar features are delicate). Quick Mode auto-selects based on image sharpness analysis. |
| Output Format | 16-bit PNG or TIFF | 16-bit preserves maximum tonal information. Use for further processing in other software. |
| Sigma Threshold | 2.5 (default) | Lower to 2.0 for severe artifact contamination. Raise to 3.0 for clean data with subtle features. |
Capture Settings Reminder
For best results with Sun, capture at 80-150 fps with 1-5ms exposure and Low-Medium (120-250) gain.
Tips for Best Results
Capture Tips for Sun
- SAFETY FIRST: Use Baader solar film, Herschel wedge, or solar telescope only
- Image early morning (6-9am) when seeing is often best
- For granulation: use green or continuum filter for best contrast
- Process gently - solar features are subtle and easy to over-sharpen
Processing Tips
- Start with Quick Mode to see baseline results
- Use Advanced Mode to fine-tune wavelets and sharpening
- Export as 16-bit TIFF for maximum quality
- Compare different algorithms to find your preference
Common Mistakes to Avoid
- •Don't over-sharpen - it creates artifacts and noise halos
- •Don't stack 100% of frames - quality matters more than quantity
- •Don't capture during poor seeing - wait for stable air
- •Don't forget to let your telescope acclimate to outside temperature
Frequently Asked Questions
Common questions about planetary video stacking and processing.
Related Guides
Explore more tutorials to expand your planetary imaging skills.
Sigma-Clip Stacking for Other Planets
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