I wrote the script CatalogStarGenerator the last year to generate a "copy" of an image without imperfections (geometric distortions, gradients, etc) using data from a catalog . A few weeks ago there was a request for an script with similar functionality so I have decided to publish it. For this, I had to modify it to implement a configuration dialog and allow setting manually the geometry.
The script tries to simulate an star field where the brightest stars are saturated and the dimmest are drown out in the sky background. The following parameters can be configured:
- Geometry: The geometry of the image can be a copy of the geometry of the active window (only when it has been plate solved and has WCS coordinates) or can be defined by the user. The geometry of the image is defined by the coordinates of the center, the resolution or focal, size in pixels and rotation. It is also important to define the epoch when using a catalog with the proper motion of the stars.
- Catalog: The list shows all the catalogs available in AnnotateImage. Only the catalogs with stars should be used.
- Saturation magnitude: The stars with a magnitude less than this value will be saturated. This value is necessary to limit the dynamic range of the image.
- Maximum magnitude: This parameter limits the magnitude of the stars read from the catalog.
- Background magnitude: This is the magnitude of the sky background. This value is necessary to limit the dynamic range of the image.
- PSF model: The script has implemented Gauss and Moffat Point Spread Functions. For both it is possible to choose the FWHM of the distribution. For Moffat there is an additional beta parameter.
- Generate noise: When this option is selected, noise is added to the image using an uniform distribution.
Since the script has not the limitations of a CCD camera (especially the well capacity or dynamic range) it is possible to generate very high dynamic range images. In this case ScreenTransferFunction has not enough precision to stretch the image. This happens when the difference between the background and saturation magnitudes is more than 10. The script warns when this happens. In this case if it is necessary to stretch the image for visualizing it, the best method is to open STF, apply the autostretch, drag the STF to the HistogramTransformation, apply the HT to the image and reset the STF. This method is useful for any HDR image.
I have also a couple of improvements in AnnotateImage:
- Graphics scale: This slider modifies the size of all the elements in the image at the same time. It is useful for applying the same annotation to images of different size. If the image is very big, the annotation can be too small. Increasing the "graphics scale" parameter the texts and markers are drawn bigger.
- Preview: The preview button opens a window with a previsualization of the annotation. The preview window can be resized, zoomed (using the toolbar or with the mouse wheel), and scrolled dragging the cursor. The preview caches the data from the catalogs so doing several tries for adjusting the annotation parameters is faster with the preview than before.
Latest versionThis message will be kept updated with the latest versions of the scripts:
- ImageSolver v1.7.2
- AnnotateImage v1.5
- CatalogStarGenerator v0.1.1
