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主题:[翻译]ASTROMETRICA的设置部分

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[翻译]ASTROMETRICA的设置部分  发帖心情 Post By:2007-01-29 20:29:18

Settings - Program 设置 - 程序
This tab sets the parameters for the object detection, reference star matching, and data reduction. Like the values specified in the CCD-tabsheet, you must set these values carefully to optimise the performance of program on your images.
本标签栏用来设置有关目标检测,参考星匹配以及天文数据归算的有关参数。想前一个关于CCD的标签一样,你需要仔细设置好这些参数才可以使本程序更好的运行和使用。


Object Detection 目标检测
The values specified in this section are used by the software to recognize objects (stars, minor planets, or comets) in your CCD frames, and to distinguish these real objects from false detections or image artefacts.
在本部分设置的值将被用于软件在你拍摄的CCD图片中来鉴别目标(如:恒星、小行星或彗星),从而来与错误的识别及图片鬼影相区别。

Aperture Radius: The radius of the synthetic aperture around the brightest pixel (the approximate center of each detection). All pixels within the aperture are used by the software to determine the centroid and flux of the object. Choose a size large enough that the peak of the PSF of the stars will be within the aperture, but small enough to resolve close pairs of stars. Generally, an aperture radius of two to three times the FWHM of the PSF is a good value. As a start, choose the radius by visually fitting the colored circles that appear after the data reduction.
孔半径:在最亮的像素附近的范围(自动检测的目标近似中心)。在这个半径内的所有像素都被软件用以识别其目标等效中心及光亮度。设置足够大的值,从而可以使恒星的点扩展函数范围在此半径之内,单也要小到足以区分密近双星。一般的,孔半径设置为点扩展函数的半宽值的两到三倍比较好。对于新手,可以直接看经过数据归算后的彩色圈的半径来设置。

Detection Limit: The minimum signal to noise ratio (SNR) required for the central pixel. The software will try to fit a stellar profile any time it finds a pixel with a SNR above the limit set here. A value of 4.0 to 5.0 is recommended. For noisy images, or images without proper calibration, you may want to increase the value to avoid spurious detections. You can set the value as low as 3.0 if you want to detect very faint objects if you use clean, well calibrated images.
探测范围:亮度中心的信噪比。如果软件发现一个像素的信噪比高于这个值,软件将试图将其与一颗星体做对应。在这里赋值为4.0或5.0是比较推荐的。对于噪点比较多或未经过适当定标的图片,你需要适当将此值设置高一点用来避免错误的目标识别。如果你的图片噪点少且定标准确,你可以将此值设置为3.0或更低用于检测更暗的目标。

Minimum FWHM: The minimum FWHM for real objects. And detections with a FWHM lower than the value specified here will be rejected. This will prevent the software from accepting hot pixels, random background noise peaks or cosmic ray strikes as real objects. A value of 1.0 will effectively reject hot pixels and most cosmic ray strikes from being detected. Depending on the scale of your images and the FWHM of real objects in your images, you may want to raise that limit to exclude further noise sources, such as clusters of hot pixels or bumps in the background. For example, if real objects in your images typically have a FWHM of 4", and the scale of your CCD images 1.5"/pixel, you may want to set the minimum FWHM to 2.0 pixels (corresponding to 3"). The maximum FWHM allowed, by the way, is assumed by the software to be the diameter of the aperture, as specified by the aperture radius described above.
最小的半最大值宽度:对真实目标的最小的半最大值宽度。如果一个目标的半最大值宽度小于此值,自动检测将不做检测。这个设置将对软件排除热噪点、背景噪声尖峰以及宇宙射线有用。设置此值为1.0将有效的排除热噪及宇宙射线。基于你的图片大小与目标半最大值宽度的大小比例,你可以将此值设置更高些用于检测剔除更多的噪音,比如一堆热噪点或连续的宇宙射线撞击。举个例子,如果你的目标的典型的半最大宽度是4",你的CCD图片像素比例为1.5"/像素,你可以将最小的半宽值设置为2.0像素(也就是3")。半宽值的最大值是上面提到的孔半径的直径。



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  发帖心情 Post By:2007-01-29 20:29:37

PSF-Fit RMS: The maximum RMS for the difference between the model PSF and the actually fitted profile. In other words, this value sets a limit on how much a real detection may differ from the assumed PSF. A value of 0.25 is usually a good starting point. Brighter stars will generally have a much lower RMS, but fainter objects will show larger values.
点扩展函数的适合均方根:对于模拟点扩展函数与真实的适合的剖面图之间的不同,软件所使用的均方根的最大值。意思是,对于不同的模拟点扩展函数究竟什么的目标才能被判断为真实目标,本值提供了一个限制值。对于新手,值0.25是被推荐的。亮的恒星通常有一个比较低的均方根,而暗的目标则具有较大的均方根。

Search Radius: The search radius, in pixels, used by the software when it tries to match detections on the individual images. Sources for which the position does not change by more than the value specified here will be considered as stars by the software, whereas minor planets or comets must move by more than this value from one image to the next to be recognized as moving objects by the moving object detection routine. The positions determined for brighter objects will generally not vary by more than a small fraction of a pixel from one image to the next, but you may want to set a larger value to accept more variation for fainter sources. In most cases, a value corresponding to about 1"-3" will be useful.
搜索半径:以像素为单位的搜索半径,用以对单个图片的自动目标检测。没个目标位置的各图片移动位置不超过此值将被视为恒星,否则则视为小行星或彗星。对于一个比较亮的目标,此值一般不会超过一个像素,你当然也可以将此值设置大一点,用来检测更暗的目标。一般情况下,此值设置在对应1"-3"比较合适。

Tip:After you have successfully completed data reduction on several images, you can click on various (bright and faint) sources in the image. The software will display the SNR, FWHM and RMS values found. You may want to use this information to fine-tune the settings specified here.
技巧:在你成功进行天文数据归算后,你可以用鼠标点击不同的目标(亮的和暗的)。软件将显示它们的信噪比,点扩展函数和均方差值。你可以参考这些值来进行设置。

Plate Constants底片常数
Using the radio buttons in this section, you can set the software to use linear, quadratic or cubic fits for the plate constants. Small field CCDs usually require no more than a linear fit. Using fits of a higher order always decreases the residuals for the reference stars, but unless the variation of the quadratic and cubic terms from one image to the next is significantly smaller than the value of these coefficients, a linear solution is probably a more accurate representation of the true plate constants than a high order fit. Furthermore, note that a reliable determination of higher orders in the plate constants is only possible if there are many dozens of reference stars available for the solution.
使用本类里的单选按钮,你可以选择使用底片常数的一次、二次或三次拟合。小视场CCD一般选择一次线性拟合,使用高次拟合可以减少参考星匹配的误差,但是除非选择二次或三次拟合可以很明显的减小误差,否则请最好使用一次拟合。而且,值得注意的是,要使用高次拟合,你必须有足够多的参考星可以获得才有意义。

Note: If you select a quadratic or cubic fit, the software will automatically switch to a linear fit if less than 12 reference stars are available. If you select a cubic fit, the software will switch to a quadratic fit if less than 20 reference starshave been included in the solution.
注意:若你选择了高次拟合,如果你的参考星数目小于12颗,软件将自动转换为一次拟合。如果选择一个三次拟合选项,如果你的参考星数目小于20颗,软件将自动转换为二次拟合。

Residuals误差
In this section, you can set a limit to the astrometric and photometric residuals of the reference stars. Those stars that exceed the limits set here will be rejected from the data reduction process.
在这里,你可以设置一个有关参考星的天文测量和光度测量的误差值。那些超过此值的目标将被拒绝接受天文数据归算处理。

Astrometric Limit: The maximum residual in the place of a reference star, specified in arc seconds. Any reference star that if found to show larger residual in either Right Ascension or Declination will be rejected from the astrometric solution.
天文测量误差极限:参考星位置对应的最大误差,用角秒表示。任何一个参考星的赤经或赤纬偏差超过这个值将被拒绝进行天文测量处理。

Photometric Limit: The maximum residual in the magnitude of a reference star. Any reference star that if found to show larger residual in the magiutude will be rejected from the photometric solution.
光度测量误差极限:参考星亮度对应的最大误差,任何参考星的亮度的误差超过此值将无法进行光度测量。

Star Catalog星表
This section is used to select the source of the reference stars used during the data reduction process. Using the combo box, you can choose between different star catalogues (USNO-A2.0, USNO-SA2.0, USNO-B1.0 or UCAC 2) supported by Astrometrica. Note that the USNO-(S)A2.0 and the UCAC 2 need to be stored on a lokal hard disk, CD or DVD (with the location of the files specified in the Environment tab sheet of the Settings dialog). The USNO-B1.0, on the other hand, is not distributed on some media, so Astrometrica will automatically connect trough the Internet to download the reference star data if you select this catalogue.
本选项将用来指定用以进行天文数据归算的参考星对应星表。使用下拉选框,你可以选择本软件支持的不同的星表(USNO-A2.0, USNO-SA2.0, USNO-B1.0 或 UCAC 2)。需要注意的是,USNO-(S)A2.0 和 UCAC 2星表需要安装在本地硬盘或CD或DVD上(需要在设置对话框的环境标签中指定)。另一方面,如果你选择了使用USNO-B1.0星表,由于其没有在媒体上发布,所以软件可以自动连接互联网并下载参考星数据。

Note: The UCAC 2 covers the sky from the south celestial pole up to a declination of about 45°. If the software notes that no UCAC 2 reference stars are available because the image to process is from a region not currently covered by the UCAC, it will ask the user to access the USNO-B1.0 instead.
注意:UCAC 2星表只覆盖从南极到赤纬45度的范围。如果软件提示没有参考星可用,那表示你所需要的区域载UCAC星表中还没有覆盖,软件将要求你用USNO-B1.0星表数据来代替。

Upper Limit: The upper limit for the magnitude of reference stars. If the field is rich in bright stars, the reference star match can fail because the brightest stars from the catalog (which are used to match the catalog to the image) are saturated in the image and are therefore not detected by the software. To avoid this problem, you can set the upper magnitude limit to approximate the magnitude where the stars in the CCD frame are saturated.
最亮星等极限:参考星的最亮的星等。如果拍摄的区域有很多亮星,参考星匹配可能失败,因为那些亮星已经暴光饱和从而使软件无法检测出来。为了避免这个问题出现,你可以设置这个最亮星等极限值为本图片的接近亮度饱和的星体的亮度。

Lower Limit: The lower limit for the magnitude of reference stars. When the field is rich in stars, you might want to exclude the faint (potentially less precise) reference stars by specifying a lower limit. (But note that the settings in the ''Residuals'' group, described above, will automatically reject reference stars with large residuals.) You can also avoid reading large numbers of faint reference stars from the star catalogue which are not detected in your images by specifying the approximate limiting magnitude of your images here.
最暗星等极限:参考星的最暗的星等。当你拍摄的图片区域中有非常多的星体,你也许想拒绝那些暗弱的(往往可能是不够精确的)参考星,就可以来设置这个值。(但请注意在上面提到的误差选项中,如果参考星的误差超过设定的值,天文数据归算将自动决绝匹配参考星。)

Note: The lower magnitude limit will also be set as a constraint for the USNO-B1.0 online query. It is recommended to set a reasonable magnitude limit (for example, 18mag or so) to limit the size of the data to download. Also note that the USNO-B1.0 query is limited to 9999 stars by default, and if a faint magnitude limit is set, the query will possibly abort due to that limitation, resulting in reference star data covering only part of the field. (Note that data for 9999 stars correspond to a data volume of about 1.7 MB.)
注意:最暗星等极限在使用USNO-B1.0星表的时候一定要设置,这对下载的数据量起决定作用(应该设置合适的值,比如18等)。而且,你应该知道,USNO-B1.0星表只允许最多下载9999颗星的数据,如果你设置了过低的极限星等,那么下载申请将被忽略,导致参考星只覆盖图片的一部分。(9999颗恒星数据大概有1.7MB大小)

Reference Star Matching参考星匹配
In this section, you can define various settings used by the software when it tries to match the stars detected in the image with the reference star data read from the star catalogue.
在这一部分,你可以定义多种设置来配合参考星的匹配。
Number of Stars: The number of stars from the image and from the catalogue, respectively, that will be used for the pattern matching. The software will use the brightest stars in the image and in the star catalogue for the matching routine. When using a star catalogue that is complete down to a certain limiting magnitude (i.e., the USNO-A2.0 or the UCAC ), a small number of stars (10 to 30) is usually sufficient. When using the USNO-SA2.0, which is only a subset of mainly faint stars, a higher number of stars is required, as many of the brighter stars in the image will be missing in the catalogue. As a crude rule of thumb, the number of stars used for the match usually is between 10% and 50% of the stars detected in the image. As a starting value, you may try to set this to 50. Note, however, that the matching algorithm is of quadratic complexity, which means that it will take about four times longer when the number of stars used for the match is doubled. If you can set the number of stars to 0, the software will not attempt to match the reference stars automatically, but rather asks the operator to match the stars manually.
星数:用以进行匹配的恒星的数目。软件将使用图片和星表中最亮的恒星进行匹配。当使用的星表是那种完全限定在某极限星等之下的数据的(比如:USNO-A2.0或UCAC星表),一个比较小的匹配星数目就一般足够了。当使用USNO-SA2.0星表的时候,由于它仅仅是在某极限星等之下亮度恒星的子集,这就需要设置更多的匹配星数目。因为有些亮的恒星可能并不包含在该星表中。出与经验,用于匹配的恒星数目一般在所有检测到恒星的10%至50%。作为一个初始值,你可以将其设置为50。注意到毕竟匹配程序的运算属于二次运算方式,所以如果将这里的值每提高一倍,所需要四倍的时间用于处理。如果你将这个值设为0,软件将不对参考星自动检测,操作者需要手动对其进行匹配。

Search Radius: The search radius, in pixels, used by the software when it tries to find the stars listed in the reference star catalogue in the image(s). If a star is located within the search radius from the predicted position, the software assumes that this star is identical with the star listed in the catalogue. It is recommended that you use a search radius is set to a value corresponding to a few arc seconds. If larger values are used, the software will more frequently find stars within the search radius which are not identical to the reference stars it is searching for, causing the reference star match to fail completely in some cases.
搜索半径:以像素为单位的搜索半径。是软件进行参考星自动匹配的搜索半径。如果在预定位置的搜索半径内有对应星,软件将设定这就是星表所对应的参考星。建议你使用合适的搜索半径,如果你使用太大的搜索半径,软件将在搜索半径内发现多个目标目标从而使其无法正确的与星表对应,而且甚至可能是匹配发生错误。
Image Alignment图片对齐定位
In this section, you can define various settings used by the software when it tries to align the individual images for data reduction or for blinking.
在这部分,你可以定义软件在天文数据分类或动画时需要对齐的图片参数。
Number of Stars: The number of stars from each image that will be used for the pattern matching. The software will use the brightest stars in the images for the alignment routine. As the inidividual images are probably very similar, the number of stars required to align the images is usually small, and a number of 10 or 30 is probably sufficient.
星数:匹配所需要的星数。软件将使用最亮的星用于对齐操作。如果图片拍摄的非常相似,用于对齐的星数可以设置的更少些,比如10或30也许就足够了。

Alignment Area: The size of the area, in pixels, used by the software to align the images for blinking and for finding fixes objects (stars) during data reduction. It is recommended to enter a value of zero to use the whole image for that process. If you have very large images, you can speed up blinking and data processing by specifying a smaller area, that, however, alwasys needs to include enough stars to enable the software to align the images. For example, wehn using 2048 x 2048 images, you may want set this value to 1024, and the software will only scan the central 1024 x 1024 pixles (i.e., one fourth of the whole image) to align the images.
对齐区域:在软件进行动画或天文数据归算的时候用于对齐图片的区域(以像素为单位)。如果在这里输入0,将使用全部图片进行对齐操作。如果你的图片很大,你可以在这里指定一个小的区域来加速动画及天文数据处理,这个区域应该有足够的星用来对齐。比如,你的图片如果是2048 x 2048大小的,你可以在这里设置1024,软件将只对图片中心部分1024 x 1024像素大小的区域(全图的四分之一)进行对齐操作。

MPC Report MPC报告
In this section, you can set some options for the MPCReport file created by the software.
Include Magnitude: When this option is checked, the MPCReport file will include magnitudes. If this is not checked, no magnitudes will be listed.

Position to 0.001s/0.01": Usually, Rights Ascension and Declination are given to 0.01s and 0.1", respectively, in the MPC Report file. When this option is checked, the software will write the Right Ascension to 0.001 seconds, and the Declination will be given to 0.01". Please note that the absolute positions derived by the software would, in almost any case, not justify to include these extra digits! However, if you are interested in relative positions (for example, during last minute astrometry for stellar occultations), this information might be of some use.

Magnitude to 0.01mag: Usually, the magnitude is given to 0.1mag in the MPC Report file. When this option is checked, the software will write the magnitude to 0.01mag. Please note that the absolute magnitude derived by the software would, in almost any case, not justify to include these extra digits! However, if you are interested in relative magnitudes of bright targets, this information might be of some use.

Related Topics: 相关主题:

Settings - General 设置-概要
Settings - Site 设置-站点
Settings - CCD 设置-CCD
Settings - Environment 设置-环境
Settings - Internet 设置-国际互联网

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[ Commands 命令| Client Windows 交互窗口| Dialog Boxes 对话框]



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  发帖心情 Post By:2007-01-30 11:53:15

谢谢,认真学习一下。

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[翻译]ASTROMETRICA的设置部分








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