Wide-area astronomical image global enhancement method

Abstract

The invention discloses a global enhancement method for a wide-area astronomical image. The method comprises the following steps: carrying out high-frame-frequency image acquisition on a starry sky area; converting the reference star from a star catalogue position to an observation position, and resolving a linear negative film model; geometric distortion correction is carried out based on the resolving result; based on the image after geometric distortion correction, matching and identifying a reference star in a full view field, and obtaining celestial coordinate information of all fixed star images in the view field; on the basis of celestial coordinate information, correcting a poorer astronomical effect of the astronomical image, establishing an ideal coordinate system taking the center of a view field as a tangency point, and projecting a time sequence observation image to the ideal coordinate system; translating the processed graph, accumulating all translated images, and averaging all accumulated pixel positions to realize image superposition enhancement, thereby effectively improving the dynamic range of a detector and the detection capability of a wide-area astronomical observation system; and meanwhile, the signal-to-noise ratio of the astronomical image can be effectively improved, and the astronomical image centering and light measuring precision can be further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of astronomical image processing, and in particular to a global enhancement method for wide-area astronomical images. Background Art

[0002] Limited by the detector's dynamic range, it's impossible to improve detection capabilities by infinitely delaying exposure time. Bright stars are more susceptible to saturation, while faint stars suffer from insufficient signal-to-noise ratio. Short-exposure stacking is the most effective means of improving the detector's dynamic range and the optical system's detection capability. Image shift stacking enhancement requires high-precision registration of the target within the image sequence. However, wide-area observation images suffer from astronomical and instrumental distortion, making global image registration difficult. Therefore, a global enhancement method for wide-area astronomical images is urgently needed to address these issues. Summary of the Invention

[0003] The purpose of the present invention is to provide a global enhancement method for wide-area astronomical images, which can effectively solve the problems existing in the above-mentioned prior art.

[0004] To solve the above technical problems, the present invention adopts the following technical solution: a global enhancement method for wide-area astronomical images, comprising the following steps: S1, collect high frame rate images of the starry sky area; S2. Convert the reference star from its catalog position to its observed position and solve the linear film model. This involves solving the mapping relationship between the reference star's celestial coordinates and the image pixel coordinates. Theoretically, the celestial sphere and the image plane only have a linear relationship of translation and rotation. Therefore, the position residual of the star image after model mapping is the geometric distortion component. S3. Based on the solution results, the residual mean of all star images within a preset range is calculated and 3 sigma iterative elimination is performed. The distortion amount of any point in the field of view is calculated based on the statistical results to perform geometric distortion correction; S4. Based on the geometric distortion-corrected image, match and identify the reference stars in the entire field of view to obtain the celestial coordinate information of all stars in the field of view; S5. Based on the collected images and the celestial coordinate information of the stars, perform the following processing: Correction for poor astronomical effects of the stars; Establish an ideal coordinate system with the center of the field of view as the tangent point, and project the time-series observation image into the ideal coordinate system; S5. Shift the processed graphics, accumulate all the shifted images, count the number of accumulations at each pixel position, and take the average value of all the accumulated pixel positions to achieve image superposition enhancement.

[0005] Preferably, the image of the starry sky area is captured at a rate of not less than 10 Hz.

[0006] Preferably, the collected multiple frames of images are preprocessed, and the entire image is median filtered through a window that is more than twice the diameter of the star image to filter out the star image (high-frequency signal) in the image, thereby obtaining a background image containing low-frequency signals such as thin clouds and optical system vignetting. The background image is subtracted from the original image to remove low-frequency background fluctuations such as thin clouds and optical system vignetting, as well as fixed pattern noise such as dark current.

[0007] Preferably, star detection is performed on the collected images: Calculate the background mean and background noise of the image, and perform global binary segmentation on the image based on the statistical values; The processed binary image is used to mark the connected components; For the connected domain marking results, perform star region statistics and output the results.

[0008] Preferably, matching and verifying reference stars within the full field of view includes: Based on the initial pointing value information of the collected image, the relevant area is retrieved in the star catalog to form a navigation star catalog; Based on the processed navigation star catalog, a triangle arc length library is constructed; Based on the star detection results, an observation triangle library is constructed; The principle of congruent triangles is used to match the navigation star library with the measured image to obtain the celestial coordinate information of all stars in the field of view.

[0009] Preferably, corrections are made to the poor astronomical effects of the star image, including corrections for poor atmospheric refraction, specifically by: Calculate the target's observation direction vector : ; in, is the direction vector of the target in the absence of atmosphere. When j=0 and i, they represent the viewing direction vector of the center of the field of view and the observed target i in the true equatorial coordinate system, respectively. j=p represents the true direction of the celestial pole, and j=z represents the viewing direction vector of the zenith in the true equatorial coordinate system. is the apparent zenith distance of the target, defined as the direction vector of the instantaneous zenith View direction vector to the target The angle between is the target atmospheric refraction angle; ; Based on the observation direction vector , calculate the polar coordinates of each pixel in the observed image and ,in: ; ; ; ; and respectively The great circle arc and tangent unit direction vector of is a vector The direction vector of express The point of express The point of Based on polar coordinates and The polar coordinate changes at the observation time are calculated by the difference calculation and , and using polar coordinate transformation and Make corrections.

[0010] Preferably, the correction of the poor astronomical effects of the stars also includes correction of poor aberration, specifically: Calculate the observation direction vector after being affected by aberration: ; ; in, is the direction vector of the observer's velocity, is the direction vector of the photon arrival at the stationary observer, is the deflection angle, is the observer's speed, D is the distance from the point of arrival of the photon; The celestial coordinates corresponding to each pixel are calculated based on the film model. The differential light aberration at each pixel position in the field of view is calculated using a theoretical model based on the celestial coordinates to correct this effect.

[0011] Preferably, the ideal coordinate system is established as follows: a rectangular coordinate system is established on the film with point C as the origin, and the vertical axis is The projection of the declination circle, with the direction of increasing declination as the positive direction; the horizontal axis Perpendicular to Axis, take the direction of increasing right ascension as positive; Among them, the ideal coordinates of the stars in the coordinate system ( , ) and its equatorial coordinates There is a one-to-one correspondence, and the corresponding relationship is: ; is the equatorial coordinate of the tangent point between the telescope field plane and the celestial sphere; The formula for calculating the equatorial coordinates from the ideal coordinates is: .

[0012] Preferably, the film model parameters are calculated by observing dense star fields, and after correction for geometric distortion and poor astronomical effects, the film model parameters are described by 4 parameters or 6 parameters; the solution formula is: .

[0013] Preferably, the graphic is translated, including: (1) Using the bright stars in the image as reference, calculate the translation and rotation of the time series image relative to the reference image; (2) Determine the sub-pixel translation dx and dy of the image, and create a blank image with the same size as the reference image to store the translated image; (3) Calculate the position of each pixel in the original image after translation; for each pixel position (x, y), the position after translation is (x+dx, y+dy); (4) According to the pixel position after translation, find the corresponding adjacent pixels on the original image, use the bilinear interpolation method to obtain the weights of the four pixels adjacent to the target position, multiply the values of the adjacent pixels by the corresponding weights, and accumulate the results to calculate the pixel value after translation; (5) Assign the calculated translated pixel value to the corresponding position of the blank reference image, repeat steps (2) to (4), process all pixels, and complete the image translation.

[0014] Beneficial effects: The present invention performs geometric distortion correction before matching and authentication to match more reference stars, thereby calculating more accurate time-series image registration values; and corrects the poor astronomical effects of stars, eliminates the influence of atmospheric refraction and aberration, and establishes an ideal coordinate system with the center of the field of view as the tangent point, projects the time-series observation image into the ideal coordinate system, and eliminates the star path bending effect; obtains a more accurate and effective image, and then shifts and aligns the observation image at a sub-pixel scale to achieve effective accumulation of the target signal in the time-series image, and achieves the same enhancement effect at the edge and center of the observation image, effectively improving the dynamic range of the detector and the detection capability of the wide-area astronomical observation system; at the same time, the present invention can effectively improve the signal-to-noise ratio of stars, and can further improve the accuracy of star centering and photometry. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0016] In the attached figure: Figure 1 A flowchart of a method for global enhancement of wide-area astronomical images is provided; Figure 2 A polar coordinate diagram for calculating the poor atmospheric refraction according to the present invention; Figure 3 is a schematic diagram of the aberration effect of the present invention; Figure 4 Schematic diagram of the relationship between the equatorial coordinates and the ideal coordinates of the present invention; Figure 5 This is a schematic diagram of poor atmospheric refraction according to the present invention; Figure 6 Schematic diagram of the comparatively poor optical aberration of the present invention; Figure 7 Schematic diagram of the instrument distortion of the present invention (left: original star map, right: distortion modeling result); Figure 8 A comparison of the effects of conventional shift and overlay enhancement (left) and global enhancement (right). DETAILED DESCRIPTION

[0017] The following describes the embodiments of the present invention in conjunction with the accompanying drawings. The terms used in the embodiments of the present invention are only used to explain the specific embodiments of the present invention and are not intended to limit the present invention. The following describes the embodiments of the present application in conjunction with the accompanying drawings.

[0018] Example: Figure 1 As shown, a global enhancement method for wide-area astronomical images includes the following steps: S1. Capture images of the starry sky at a high frame rate (not less than 10 Hz). Preprocess the captured multi-frame images to remove low-frequency background fluctuations such as thin clouds and optical system vignetting, as well as fixed-pattern noise such as dark current. S2, performing star detection on the star map obtained after preprocessing; In this embodiment, the following method is used to perform star detection: S21, performing statistics on the background mean and background noise of the image, and performing global binary segmentation on the image based on the statistical values; S22, marking connected domains on the binary image obtained by step S21, using an 8-connectivity method; S23, performing constellation region statistics and outputting the results for the connected domain labeling result obtained by processing in step S22; S3. Match and verify the star map containing the candidate constellations with the reference star catalog, match and verify the reference stars in the entire field of view, and verify the matching and verification results; In this embodiment, the following method is used for matching and authentication: S31, based on the initial pointing value information of the collected image, searching for a relevant area in the star catalog to form a navigation star catalog; S32, constructing a triangle arc length library based on the navigation star catalog obtained in step S31; S33, constructing an observation triangle library based on the star detection results obtained in step S2; S34. Based on the principle of congruent triangles, the navigation star library is matched with the measured image to obtain the celestial coordinate information of all stars in the field of view; The following problems exist for the collected images: (1) In large-field astronomical observation images, different areas within the field of view are affected differently by atmospheric refraction, and the star image will produce angular changes relative to a certain reference point within the field of view, such as Figure 5 As shown; (2) Due to the finite speed of light and the observer's motion relative to the target celestial body, the observed direction of the celestial body deviates from its actual direction of arrival of photons; Figure 6 As shown (3) Wide-area astronomical observations have a large field of view and complex distortion patterns, so geometric distortion correction is required. (4) In fixed-pointing observation equipment, the motion trajectory of the star image is projected into the observation image as a curve, and the curvature radius of the motion trajectory of star images with different declinations in the field of view is different; Based on the above, in this embodiment, the following method is adopted: S4, based on the celestial coordinate information of the stars obtained by processing in step S3, correcting the poor astronomical effects of the stars; S41, poor atmospheric refraction correction; in this embodiment, the following symbols are defined: is the direction vector of the target in the absence of atmosphere; when j=0 and i, they represent the apparent direction vector of the center of the field of view and the observed target i in the true equatorial coordinate system respectively; j=p represents the true direction of the celestial pole, and j=z represents the apparent direction vector of the zenith in the true equatorial coordinate system; for the center of the field of view and all target stars in the field of view, the apparent direction vector mentioned here already includes the influence of aberration; since aberration does not change the rotation center of the diurnal apparent motion of the starry sky, the celestial pole direction vector here only uses its true direction.

[0019] is the observation direction vector of target j (including the influence of atmospheric refraction); Due to the influence of atmospheric refraction, the apparent direction vector of the celestial body before entering the atmosphere will become the observation direction vector , Located in Zenith direction vector The relationship between them can be expressed as follows: ; in, is the apparent zenith distance of the target, defined as the direction vector of the instantaneous zenith View direction vector to the target The angle between them. is the target atmospheric refraction angle, which can be expressed as: ; Under standard atmospheric conditions, the yellow starlight with an equivalent wavelength of about 0.57 μm , , and the corresponding refraction angle is , Rj0 is Rj when k1 and k2 are assigned values; when the apparent zenith distance is known, the above formula can be solved by iteration When the atmospheric conditions at the observation site deviate significantly from the standard state, the actual refraction amount is calculated using the following formula: ; Where T and P are the temperature and air pressure at the time of observation, respectively.

[0020] The vector expression of the target's apparent zenith distance is: ; From the above formula, the observation directions of the celestial pole, zenith and target can be calculated .

[0021] In order to describe the position of the target in the image field relative to the center of the field of view, a spherical polar coordinate system is established with the center of the field of view as the pole, referring to Figure 2 As shown, the coordinate vector is Indicates; here is the great circle length from the target image to the center of the field of view, is the angle between the image of the target and the image of the north celestial pole at the center of the field of view; Polar coordinates of the image of target i: ; ; or ; in: ; ; and respectively The great circle arc and tangent unit direction vector of is a vector The direction vector of express The point of express The direction point.

[0022] According to the polar coordinates of each pixel in the observed image and The polar coordinate change at the observation time can be obtained and After making corrections, an observation image without the influence of atmospheric refraction relative to the center of the field of view can be obtained.

[0023] S42, poor aberration correction; The influence on the observed position of celestial bodies is expressed as follows: ; ; in, is the direction vector of the observer's velocity, is the direction vector of the photon arrival at the stationary observer, is the observation direction vector after being affected by aberration, is the deflection angle, is the speed of the observer, and D is the distance from the point of arrival of the photon. Figure 3 The figure shows the principle of the effect of aberration on the target observation direction. In large-field astronomical observation images, different areas within the field of view are affected differently by aberration, and the star image will produce angular distance changes relative to a reference point within the field of view; Figure 3 From the formula for aberration, we know that on the celestial sphere, aberration shifts the observation direction of a celestial object along the great circle arc passing through the celestial object and the atlas, toward the atlas. The magnitude of this shift is proportional to the observer's velocity and the sine of the distance from the celestial object to the atlas. In a wide-field observation image, the atlas distance varies for each pixel, and therefore the effect of aberration varies. The effect of aberration on the observation position of an object within the field of view is very similar to that of atmospheric refraction, and the correction method for this effect is the same: calculate the aberration and the atlas relative to the center of the field of view based on the pixel's celestial coordinates and the aberration model, and then correct the pixel position in the image.

[0024] S5. Geometric distortion correction: In this embodiment, the following method is used to correct geometric distortion: S51. Collect a batch of dense star field observation images to ensure that the positions of the stars in the field of view have obvious changes; S52, performing star image detection and reference star matching on the observed image; S53, convert the reference star from the catalog position to the observation position to avoid distortion caused by poor atmospheric refraction and poor aberration; S54, solving the linear film model. This embodiment uses four parameters to perceive all linear and nonlinear distortion terms. S55. Based on the results of the single-frame linear film model solution, the measurement residuals of all star images with good signal-to-noise ratio and non-saturated are counted; S56, selecting a suitable image grid (a 30×30 grid is used in this embodiment), calculating the mean of all star image residuals in the grid and performing 3sigma iterative elimination; S57. The residual mean of a large number of star images in each grid can absorb the random error of position measurement, thereby standardizing the position system error, which is the geometric distortion at the grid point. Figure 7 As shown in Figure 1, it is the geometric distortion modeling result of a certain optoelectronic observation system; S58. In the subsequent data processing process, based on the numerical template of geometric distortion, a method such as bilinear interpolation or bicubic spline interpolation is used to calculate the distortion amount of any point in the field of view to complete the final geometric distortion correction; In another embodiment, before the matching verification in step S2, the geometric distortion correction in step S5 is performed to calculate a more accurate temporal image registration value; the geometric distortion correction in step S5 can be iteratively performed with the reference star matching verification to match more reference stars and avoid areas where the correction effect is not achieved due to lack of reference stars. Better distortion correction can match more reference stars, and generally 2 to 3 iterations are required for stability. After correcting for telescope image distortion, poor atmospheric refraction, and aberration, this embodiment establishes an ideal coordinate system with the center of the field of view as the tangent point. The horizontal and vertical axes of this coordinate system are the directions of increasing right ascension and declination, respectively. When the time-series observation images are projected onto this ideal coordinate system, the motion trajectories of star images caused by the Earth's rotation become straight lines in the ideal coordinate system, eliminating the effect of star path curvature. The process of establishing the ideal coordinate system is as follows: The imaging law of astronomical telescopes follows the law of centroid projection, so the ideal coordinate system is defined as a rectangular coordinate system on the film; Figure 4 In the equation, CO is the optical axis of the telescope, which is perpendicular to the focal plane and has a focal length of F. The photographic plate is placed on the focal plane, and its center is C. When CO is extended toward the celestial sphere, its intersection with the celestial sphere is C′, which is the tangent point between the telescope's field of view and the celestial sphere. Its equatorial coordinates are ; On the film, a rectangular coordinate system is established with point C as the origin, and the vertical axis is The projection of the declination circle, with the direction of increasing declination as the positive direction; the horizontal axis Perpendicular to Axis, take the direction of increasing right ascension as positive; C- It is called the ideal coordinate system; for a piece of film, the ideal coordinate system is unique, and the ideal coordinates of the star image in this coordinate system ( , ) and its equatorial coordinates There is a one-to-one correspondence and the following relationship exists: ; The formula for calculating the equatorial coordinates from the ideal coordinates is: ; Because the measured coordinate axes are not completely parallel to the coordinate axes of the ideal coordinate system, the scales of the two coordinate systems are also different. Therefore, it is necessary to observe dense star fields and calculate the film model parameters using the following formula. After correcting for image field distortion and poor atmospheric refraction and aberration effects, the measured coordinates and the ideal coordinates should be in a linear relationship. The film model parameters can be described by 4 parameters or 6 parameters. .

[0025] S6, sub-pixel scale image translation registration; This embodiment uses the following method to perform translation registration: S61. After completing the astronomical distortion and instrument distortion calibration, the time-series image registration can be completed through simple translation and rotation. Since the time-series image intervals are short, most of the bright stars in the images will not be out of the field of view. Using the bright stars in the images as references, the translation and rotation of the time-series images relative to the reference image are calculated. S62. Since the translation and rotation amounts are not integer pixels, they must be completed at the sub-pixel scale. The key to sub-pixel image shift and superposition is to make discrete pixels continuous, or to understand it as translating the image at the sub-pixel scale. Linear interpolation is used to complete the sub-pixel shift of the image. S63, determining the translation amounts dx and dy of the image at the sub-pixel scale, and creating a blank image with the same size as the reference image for storing the translated image; S64. Calculate the position of each pixel in the original image after translation. For each pixel position (x, y), the position after translation is (x+dx, y+dy); S65. Based on the position of the pixel after translation, find the corresponding neighboring pixels on the original image, use bilinear interpolation to obtain weights for the four neighboring pixels of the target position, and assume that the area of the entire square region is 1. The value of the point (x, y) can be used to divide the area of the block into four. The proportion of the area of each block to the total surface is the weight of its corresponding vertex. The values of the neighboring pixels are multiplied by the corresponding weights, and the results are accumulated to calculate the pixel value after translation. S66, assigning the calculated translated pixel value to the corresponding position of the blank reference image, repeating steps S63-S65, processing all pixels, and completing the image translation; S7, image stacking and enhancement; accumulating all translated images, counting the number of accumulations at each pixel position, taking the average of all accumulated pixel positions, and completing image stacking and enhancement.

[0026] Based on the above method, reference Figure 8 The figure shows the comparison between the global enhancement processing of the measured star map based on the method of the present invention and the conventional shift and superposition processing results. Figure 8 The left and right images show the stacking and enhancement results of 100 frames of time-series images. The left image shows conventional shift-stack enhancement, showing good star formations in the center of the field of view, but elongation in different directions at the edges. This is due to the failure to correct astronomical and instrumental distortion. The right image shows the global enhancement result using our method, showing good star formations at both the edges and the center of the image, achieving high-quality global enhancement.

[0027] The above describes the embodiments of the present invention in detail with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. After knowing the contents described in the present invention, ordinary technicians in this technical field can make several equivalent changes and substitutions without departing from the principles of the present invention. These equivalent changes and substitutions should also be regarded as falling within the scope of protection of the present invention.

Claims

1. A global enhancement method for wide-area astronomical images, characterized in that: The steps include: S1, collect high frame rate images of the starry sky area; S2, convert the reference star from the catalog position to the observation position and solve the linear plate model; S3. Based on the solution results, the residual mean of all star images within a preset range is calculated and 3 sigma iterative elimination is performed. The distortion amount of any point in the field of view is calculated based on the statistical results to perform geometric distortion correction; S4. Based on the geometric distortion-corrected image, match and identify the reference stars in the entire field of view to obtain the celestial coordinate information of all stars in the field of view; S5. Based on the collected images and the celestial coordinate information of the stars, perform the following processing: Correction for poor astronomical effects of the stars; Establish an ideal coordinate system with the center of the field of view as the tangent point, and project the time-series observation image into the ideal coordinate system; S6. translating the processed graphics, and accumulating all translated images, counting the number of accumulations at each pixel position, and taking an average value of all accumulated pixel positions to achieve image superposition enhancement.

2. The method for global enhancement of wide-area astronomical images according to claim 1, characterized in that: The image of the starry sky area is collected at a rate of not less than 10 Hz.

3. The method for global enhancement of wide-area astronomical images according to claim 2, characterized in that: The collected multiple frames of images are preprocessed, and the entire image is median filtered using a window that is more than twice the diameter of the star image. The stars in the image are filtered out to obtain a background image containing low-frequency signals such as thin clouds and optical system vignetting. The background image is subtracted from the original image to remove low-frequency background fluctuations such as thin clouds and optical system vignetting, as well as fixed pattern noise such as dark current.

4. The method for global enhancement of wide-area astronomical images according to claim 1, characterized in that: Perform star detection on the collected images: Calculate the background mean and background noise of the image, and perform global binary segmentation on the image based on the statistical values; The processed binary image is used to mark the connected components; For the connected domain marking results, perform star region statistics and output the results.

5. The method for global enhancement of wide-area astronomical images according to claim 4, characterized in that: Match and verify reference stars in the entire field of view, including: Based on the initial pointing value information of the collected image, the relevant area is retrieved in the star catalog to form a navigation star catalog; Based on the processed navigation star catalog, a triangle arc length library is constructed; Based on the star detection results, an observation triangle library is constructed; The principle of congruent triangles is used to match the navigation star library with the measured image to obtain the celestial coordinate information of all stars in the field of view.

6. The method for global enhancement of wide-area astronomical images according to claim 1, characterized in that: Correction for the poor astronomical effects of the star image, including poor atmospheric refraction correction, specifically: Calculate the target's observation direction vector : ； in, is the direction vector of the target in the absence of atmosphere. When j=0 and i, they represent the viewing direction vector of the center of the field of view and the observed target i in the true equatorial coordinate system, respectively. j=p represents the true direction of the celestial pole, and j=z represents the viewing direction vector of the zenith in the true equatorial coordinate system. is the apparent zenith distance of the target, defined as the direction vector of the instantaneous zenith View direction vector to the target The angle between is the target atmospheric refraction angle; ； Based on the observation direction vector , calculate the polar coordinates of each pixel in the observed image and ,in: ； ； ； ； and respectively The great circle arc and tangent unit direction vector of is a vector The direction vector of express The point of express The point of Based on polar coordinates and The polar coordinate changes at the observation time are calculated by the difference calculation and , and using polar coordinate transformation and Make corrections.

7. The method for global enhancement of wide-area astronomical images according to claim 1 or 6, characterized in that: Correction for the poor astronomical effects of the stars, including correction for poor aberration, specifically: Calculate the observation direction vector after being affected by aberration: ； ； in, is the direction vector of the observer's velocity, is the direction vector of the photon arrival at the stationary observer, is the deflection angle, is the observer's speed, D is the distance from the point of arrival of the photon; The celestial coordinates corresponding to each pixel are calculated based on the film model. The differential light aberration of each pixel position in the field of view is calculated through the theoretical model according to the celestial coordinates to correct the differential astronomical effect.

8. The method for global enhancement of wide-area astronomical images according to claim 1, characterized in that: The ideal coordinate system is established as follows: a rectangular coordinate system is established on the film with point C as the origin, and the vertical axis is The projection of the declination circle, with the direction of increasing declination as the positive direction; the horizontal axis Perpendicular to Axis, take the direction of increasing right ascension as positive; Among them, the ideal coordinates of the stars in the coordinate system ( , ) and its equatorial coordinates There is a one-to-one correspondence, and the corresponding relationship is: ； is the equatorial coordinate of the tangent point between the telescope field plane and the celestial sphere; The formula for calculating the equatorial coordinates from the ideal coordinates is: 。 9. The method for global enhancement of wide-area astronomical images according to claim 8, characterized in that: By observing dense star fields, the film model parameters are solved and, after correction for geometric distortion and poor astronomical effects, described by 4 or 6 parameters. The solution formula is: 。 10. The method for global enhancement of wide-area astronomical images according to claim 1, characterized in that: Graphics translation, including: (1) Using the bright stars in the image as reference, calculate the translation and rotation of the time series image relative to the reference image; (2) Determine the sub-pixel translation dx and dy of the image, and create a blank image with the same size as the reference image to store the translated image; (3) Calculate the position of each pixel in the original image after translation; for each pixel position (x, y), the position after translation is (x+dx, y+dy); (4) According to the pixel position after translation, find the corresponding adjacent pixels on the original image, use the bilinear interpolation method to obtain the weights of the four pixels adjacent to the target position, multiply the values of the adjacent pixels by the corresponding weights, and accumulate the results to calculate the pixel value after translation; (5) Assign the calculated translated pixel value to the corresponding position of the blank reference image, repeat steps (2) to (4), process all pixels, and complete the image translation.

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