Stacking Calculator
Calculate SNR improvements and plan integration time for your deep sky imaging sessions.
Input Your Session Data
Horsehead, Veil, California - dim emission/reflection nebulae
Usable but noisy, consider more subs
SNR Improvement Visualization
Recommendations
- 💡Great number of subs! You can use aggressive rejection settings to remove satellites and planes.
- 💡Add ~10 more subs to reach minimum recommended integration for faint nebula.
SNR Improvement Reference
| Subs | SNR Improvement | Description | @ 120s each |
|---|---|---|---|
| 4 | 2× | 2× SNR - noticeable improvement | 8 minutes |
| 9 | 3× | 3× SNR - significant noise reduction | 18 minutes |
| 16 | 4× | 4× SNR - very clean image | 32 minutes |
| 25 | 5× | 5× SNR - excellent quality | 50 minutes |
| 36 | 6× | 6× SNR - professional quality | 1h 12m |
| 100 | 10× | 10× SNR - exceptional detail | 3h 20m |
Recommended Integration Times by Target
Understanding Stacking in Astrophotography
Why Stack Images?
A single long exposure captures both signal (light from your target) and noise (random variations). By stacking multiple exposures, the consistent signal adds up while random noise averages out, dramatically improving image quality.
The Square Root Rule
SNR improves by √n where n is the number of frames. This means diminishing returns - going from 1 to 4 frames doubles SNR, but you need 16 frames to double it again.
Key Concepts
- •Integration Time: Total exposure time across all stacked frames
- •Sub-frame: Individual exposure before stacking
- •SNR: Signal-to-Noise Ratio - higher is cleaner
- •Sigma Clipping: Rejection algorithm that removes outliers (satellites, planes)
Stacking Best Practices
📊 Quantity vs Quality
More shorter subs often beats fewer longer subs. 100×60s gives better outlier rejection than 20×300s, even with same total integration.
🎯 Match Your Target
Bright targets need less integration. Don't spend 10 hours on the Orion Nebula - use that time on fainter targets instead.
☁️ Multi-Night Sessions
Spread your integration across multiple nights. Weather, seeing, and fatigue all benefit from splitting sessions.
📁 Calibration Frames
Always capture darks, flats, and bias frames. They remove fixed pattern noise and vignetting that stacking alone can't fix.
💾 Storage Planning
A 300-frame session with a 45MP camera needs ~45GB. Plan your storage and backup strategy before imaging.
⚙️ Rejection Settings
With 50+ subs, use aggressive sigma clipping (2-3σ). With fewer subs, use gentler settings (3-4σ) to preserve signal.
Frequently Asked Questions
How does stacking improve astrophotography images?
Stacking multiple sub-frames improves signal-to-noise ratio (SNR) by averaging out random noise while preserving the consistent signal from celestial objects. SNR improves by the square root of the number of frames.
How many sub-frames do I need for astrophotography?
A minimum of 20-30 sub-frames is recommended for effective stacking and outlier rejection. For optimal results, 50-100+ subs provide excellent noise reduction. The ideal number depends on your target brightness and desired quality.
What is the best sub-exposure length?
Sub-exposure length depends on your setup: 30-60 seconds for unguided or light-polluted skies, 120-180 seconds for guided setups with moderate light pollution, and 300+ seconds for dark sites with excellent guiding.
How much integration time do I need for galaxies?
For bright galaxies like Andromeda, 1-3 hours provides good results. Fainter galaxies need 4-8 hours, while galaxy clusters may require 10-20+ hours for optimal detail.
What is SNR in astrophotography?
SNR (Signal-to-Noise Ratio) measures how much actual signal stands out from random noise. Higher SNR means cleaner images with more detail. Stacking, longer exposures, and darker skies all improve SNR.
Plan your complete imaging session: