Under-sampling astronomical image high-precision photometry method under pixel phase error constraint
By using an undersampling astrophotography method constrained by pixel phase error, stars whose centers are close to the pixel edges are selected and centered. By combining multiple exposure images, pixel phase error and random noise are eliminated, thus improving the accuracy of astrophotography.
Patent Information
- Application Number
- CN202510972359.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-15
- Publication Date
- 2025-11-04
AI Technical Summary
Under the constraint of pixel physical size, the undersampling astrophotometry method of high-resolution space optical telescopes cannot effectively eliminate the influence of pixel phase error, resulting in insufficient photometric accuracy.
By designing pixel phase error constraints, star images with an absolute pixel phase value greater than 0.2 pixels on the X-axis or Y-axis are selected for star image centering and aperture metering. Combined with multi-frame exposure observation images, systematic errors and random noise are eliminated, and metering results are optimized.
It significantly improves the accuracy of astrophotography, increasing the accuracy from 0.06 magnitude using traditional methods to 0.008 magnitude, more than doubling the accuracy.
Smart Images
Figure CN120890547A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of astronomical image photometry, in particular to an undersampling star image high-precision photometry method under pixel phase error constraint. BACKGROUND
[0002] For a high-resolution space optical telescope, under the constraint of pixel physical size, star image sampling usually cannot be fully sampled, and undersampling star image is common. For undersampling star image, the traditional photometry method only performs single-frame image photometry, or simply superimposes multiple frames of images to take the average value of photometry as the photometry result, which cannot effectively eliminate the influence of photometry pixel phase error. The more serious the undersampling degree of star image, the more significant the influence of this systematic error. Therefore, there is an urgent need for an undersampling star image high-precision photometry method under pixel phase error constraint to solve the above-mentioned undersampling star image photometry problem. SUMMARY
[0003] The purpose of the present application is to provide an undersampling star image high-precision photometry method under pixel phase error constraint to solve the problems in the background art.
[0004] To solve the above technical problems, the present application adopts the following technical scheme: an undersampling star image high-precision photometry method under pixel phase error constraint, comprising the following steps: Obtain all star images of the target star, and construct a star image dataset; Design a phase error constraint: retain star images with pixel phase absolute value greater than 0.2 pixels on the X-axis or Y-axis; Center the star images in the star image dataset to obtain the pixel phase information of the center of each star image, and filter the star image dataset based on the phase error constraint; Aperture photometry is performed on the retained star images to obtain the luminosity value of each star image.
[0005] Preferably, all star images of the target star are extracted from the observation image of the target star; the observation image is a plurality of continuous exposure observation images of the target star; the number of the plurality of continuous exposure observation images of the target star is not less than a preset number; so that the star image sample is sufficient, which is conducive to eliminating the influence of photometric random error; under the phase error constraint, star image photometry will significantly reduce the systematic error.
[0006] Further preferably, the star image of the target star is undersampling and high signal-to-noise ratio, the full width at half maximum is less than 1.5 pixels, and the signal-to-noise ratio is greater than 50.
[0007] Preferably, a two-dimensional Gaussian profile fitting method is used to calculate the pixel phase at the center of each star image.
[0008] Preferably, a preset diameter aperture is constructed with the star image center as the origin, the sum of the pixel gray values in the aperture is counted, and the average background gray value is counted, and the product of the average background gray value and the number of pixels in the aperture is removed from the sum of the pixel gray values based on the number of pixels in the aperture.
[0009] Further preferably, an aperture of 4 times the diameter of the star image is set with the star image center as the origin, the sum of the pixel gray values in the aperture is counted, and the average background gray value is counted by removing the star image reserved background by the Newton iteration method, and the aperture photometry result of the star image is: .
[0010] Preferably, the average value of all the star image brightness is calculated, and the star photometry result is optimized based on the average value divided by the average quantum response of the detector.
[0011] Beneficial effects: through in-depth research and analysis of the star image photometry accuracy and the star image centering result (star image center pixel phase), it is found that the star image center pixel phase will constrain the star image photometry accuracy, the star image photometry average value statistics is selected by using multi-frame exposure observation images and selecting star images with star image centers close to the pixel edges, and the star photometry pixel phase error is eliminated; therefore, the present application realizes the common elimination of the photometry system error and the random error by designing the phase error constraint and selecting the star image photometry average value statistics under the constraint, significantly improves the star image photometry accuracy, and for the under-sampling bright star with a full width at half maximum of 0.5 pixels, the photometry accuracy is improved from the traditional method of 0.06 magnitude accuracy to 0.008 magnitude accuracy, which has obvious improvement. BRIEF DESCRIPTION OF DRAWINGS
[0012] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, illustrate the present application together with the embodiments thereof, and explain the present application, but do not constitute a limitation of the present application.
[0013] In the drawings: Figure 1 is a flowchart of the under-sampling star image high-precision photometry method of the present application under the pixel phase error constraint; Figure 2 is a star photometry residual diagram of the present application; Figure 3 is an RMS diagram of the star photometry residual of the present application. DETAILED DESCRIPTION
[0014] The embodiments of the present invention will now be described with reference to the accompanying drawings. The terminology used in the embodiments section is for illustrative purposes only and is not intended to limit the scope of the invention. The embodiments of this application will now be described with reference to the accompanying drawings.
[0015] refer to Figure 1 A high-precision photometric method for undersampled astrophotography under pixel phase error constraints includes the following steps: Obtain all star charts of the target star and construct a star chart dataset; In one embodiment, the stellar photometric measurement is affected by a systematic error related to the position of the star relative to the pixel boundary. That is, the photometric residual decreases as the star center moves closer to the pixel edge. To eliminate this effect, all star images of the target star are extracted from the observation image of the target star. The observation image is a multi-frame continuous exposure observation image of the target star. The multi-frame continuous exposure observation image of the target star needs to meet a preset number to ensure sufficient star image samples. In one specific embodiment: 50 frames of observation images were used to measure the luminosity of the target stars; the full width at half maximum (FWHM) of the target stars was 0.5 pixels, and the signal-to-noise ratio was between 85 and 115. A total of 100 target stars were analyzed. Center all celestial bodies in the celestial dataset and filter out those that meet specific pixel phase requirements, including: Design phase error constraints: retain star constellations with an absolute pixel phase value greater than 0.2 pixels along the X-axis or Y-axis; and obtain the pixel phase information of the center of each star constellation based on the centering of all star constellations, and filter the star constellation dataset based on the phase error constraints; In one embodiment, before filtering constellations near the pixel edge, it is necessary to measure the constellation center; the pixel phase of the center of each constellation is calculated using a two-dimensional Gaussian profile fitting method.
[0016] Aperture photometry is performed on the selected star images to obtain the luminosity value of each star image. The final luminosity value of the target star is obtained by averaging to eliminate the influence of random noise.
[0017] The brightness of each selected constellation is calculated using aperture metering. Specifically, the aperture is set to four times the constellation's diameter, with the center of the constellation as the origin. The sum of the pixel grayscale values is then calculated. Additionally, the Newton-Raphson iterative method was used to remove the celestial bodies while preserving the background, and the average grayscale value of the background was calculated. If there are n pixels within the aperture, then the aperture photometry result for the star is: ; Calculate the average brightness of these stars ( ), and then divided by the average quantum response of the detector to obtain the final photometric result of the star; The photometric residual and the photometric accuracy of the star image are calculated according to the true brightness of the target star (see Figure 2 and Figure 3 ); Reference Figure 2 shows the photometric residual of the star; reference Figure 3 shows the RMS of the photometric residual of the star, that is, the photometric accuracy of the star; the circular scatter points represent the results of directly averaging the multi-frame observation images using the traditional aperture photometry processing; the triangular scatter points are the method of the present application, that is, the high-precision photometry method of the under-sampling star image under the constraint of the pixel phase error (pho); the RMS of the photometric residual of the star is calculated based on all star samples in the interval under the corresponding signal-to-noise ratio (90, 100, 110); from Figure 2 and Figure 3 It can be seen that the photometric result obtained by processing is obviously improved relative to the traditional method, and the photometric accuracy is improved from 0.06 magnitude accuracy of the traditional method to 0.008 magnitude accuracy, which is improved by nearly one order of magnitude.
[0018] The embodiments of the present application are described in detail above in combination with the drawings, but the present application is not limited to the above-described embodiments. For ordinary skilled persons in the technical field, after knowing the content recorded in the present application, they can make several equivalent transformations and substitutions without departing from the principles of the present application, and these equivalent transformations and substitutions should also be regarded as belonging to the protection scope of the present application.
Claims
1. A high-precision photometric method for undersampled celestial phenomena under pixel phase error constraints, characterized in that, Includes the following steps: Obtain all star charts of the target star and construct a star chart dataset; Design phase error constraints: retain star images with an absolute pixel phase value greater than 0.2 pixels along the X or Y axis; The star constellations in the star constellation dataset are centered to obtain the pixel phase information of the center of each star constellation, and the star constellation dataset is filtered based on the phase error constraint. Aperture photometry was performed on the preserved constellations to obtain the luminosity value of each constellation.
2. The high-precision photometric method for undersampled celestial phenomena under pixel phase error constraints according to claim 1, characterized in that: Extract all the star images of the target star from the observed image of the target star; and the observed image is a multi-frame continuous exposure observation image of the target star; the number of the multi-frame continuous exposure observation images of the target star is not less than a preset number.
3. The high-precision photometric method for undersampled celestial phenomena under pixel phase error constraints according to claim 2, characterized in that: The target star's image is undersampled and has a high signal-to-noise ratio, with a full width at half maximum (FWHM) of less than 1.5 pixels and a signal-to-noise ratio greater than 50.
4. The high-precision photometric method for undersampled celestial phenomena under pixel phase error constraints according to claim 3, characterized in that: The phase of the pixel at the center of each star was calculated using a two-dimensional Gaussian profile fitting method.
5. The high-precision photometric method for undersampled celestial phenomena under pixel phase error constraints according to claim 3 or 4, characterized in that: Using the center of the constellation as the origin, construct an aperture with a preset diameter, and calculate the sum of the gray values of the pixels within it, as well as the average gray value of the background. Based on the number of pixels within the aperture, remove the product of the average gray value of the background and the number of pixels within the aperture from the sum of the pixel gray values.
6. The high-precision photometric method for undersampled celestial phenomena under pixel phase error constraints according to claim 5, characterized in that: Using the center of the constellation as the origin, set an aperture four times the diameter of the constellation and count the sum of the pixel grayscale values within it.
7. The high-precision photometric method for undersampled celestial phenomena under pixel phase error constraints according to claim 5, characterized in that: The constellations were removed using the Newton-Raphson iterative method while retaining the background, and the average gray value of the background was calculated.
8. The high-precision photometric method for undersampled celestial phenomena under pixel phase error constraints according to claim 5, characterized in that: The average brightness of all retained stars is calculated, and the stellar photometry results are optimized based on the average value divided by the detector's average quantum response.