Night Sky Image Alignment Without Equatorial Mounts
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Solution Overview
Problem
Night sky images captured with fixed image capture devices suffer from blurring due to Earth's rotation during long exposures, and using equatorial mounts to compensate for this is costly and complicated.
Innovation Solution
Determine a center of rotation by tracking stars across multiple images and aligning them using the intersection of perpendicular bisectors, then rotate and combine the images to generate a high signal-to-noise ratio night sky image without the need for expensive equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If long exposures are used to capture night sky images, then image detail is improved, but star targets become blurred due to Earth's rotation
Solution Approach 1:
Instead of rotating the camera to track stars during long exposure, the patent captures multiple short-exposure images and rotates them computationally in reverse direction to compensate for Earth's rotation. This inverts the approach from mechanical tracking to digital post-processing rotation.
Solution Approach 2:
The patent performs preliminary actions by capturing multiple short-exposure images before combining them. The center of rotation is determined in advance, and images are pre-rotated to align stars before final combination, preventing blur rather than correcting it afterward.
2Reliability
If equatorial mounts are used to track stars during long exposures, then star target clarity is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical equatorial mount system with a computational approach. Instead of using motors and mechanical tracking mechanisms, the system uses image processing algorithms to rotate and align multiple short-exposure images, substituting mechanical complexity with digital processing.
Solution Approach 2:
The patent creates a computational model of the star field's rotation by determining the center of rotation from multiple images. This virtual copy of the rotational motion is then applied in reverse to align the images, replacing the need for physical tracking mechanisms.
3Measurement precision
If multiple images are captured and combined, then signal-to-noise ratio is improved, but image alignment difficulty increases due to star position changes
Solution Approach 1:
The patent uses star positions as feedback to determine the center of rotation. By analyzing the apparent motion of stars across multiple images, the system calculates the rotation center and uses this information to properly align and combine the images, creating a closed-loop alignment process.
Solution Approach 2:
The patent changes the parameter of rotation angle for each image based on its position in the sequence. By calculating the appropriate rotation angle for each image relative to the center of rotation, the system dynamically adjusts alignment parameters to compensate for Earth's rotation during the capture sequence.
Data Source
AI summary
An image capture device may capture images of the night sky while fixed in place. Changes in positions of stars depicted within the images may be used to determine the center of rotation for the images. The images may be rotated about the center of rotation and combined to generate a night sky image with a higher signal-to-noise ratio.