MultiCombine Plugin for CCDSoft Version 0.5a, May 11, 2003 Overview ======== The MultiCombine plugin provides fast average, median, and trimmed-mean (also known as "sigma") combine functions as a CCDSoft plugin. Primary features include: - Pedestal-aware averaging and median capabilities that are faster than the default versions in CCDSoft - Single- and double-pass trimmed-mean combines for better signal preservation than simple median filtering but with outlier rejection that averaging doesn't provide - The ability to restore a fixed pedestal into the combined image - Omission of zero-value pixels in averaging combines (zero- value pixels almost always are generated by alignment routines, and should therefore not be included when performing pixel math System Requirements =================== This plugin requires CCDSoft Version 5 from SoftwareBisque, release 5.00.99. If you do not have 5.00.99, version updates are available from Software Bisque's Web site: http://www.bisque.com/Products/CCDSoft/CCDSoftV5Update.asp http://www.bisque.com/hotfixes/ Installation ============ Double-click the mcSetup.exe application, and follow the setup prompts. The plugin and support files will be installed automatically. Instructions for Use ==================== Because of how CCDSoft currently handles plugins, an image file must be open before you can access the MultiCombine plugin (this is expected to change in a future release of CCDSoft). You must therefore open a dummy (throwaway) image before you begin your combining; the image will be overwritten with the output of the combine. If you don't want to create a dummy image or are concerned about accidentally overwriting something important, I have a created a dummy image that you can download: http://www.mightyatom.com/astronomy/testImg.fit Open the dummy image, and then choose the Image->Plug Ins-> MultiCombine... menu item. When the dialog box comes up, first enter the path to the folder of images you wish to combine in the "Folder to combine" text box, or click the "Choose Folder..." button. Choose the desired combine method from the "Combine Method" drop-down menu. The combine methods work as follows: - Average: Output pixel is the average of the pixels in the input images - Median: Output pixel is the median (middle) value of the pixels in the in the input images - Single-pass trimmed mean: Output pixel is the average of the pixels in the input images, omitting pixels that fall more than the specified number of standard deviations above or below the mean of all the pixels - Double-pass trimmed mean: Output pixel is the average of the pixels in the input image, omitting pixels that fall more than the specified number of standard deviations above or below the *trimmed mean* as calculated in the single-pass algorithm If you are using a trimmed mean combine, you can choose the rejection boundaries for both bright and dark (high and low) pixels. These boundaries are delineated in standard deviations from the mean. If you set these values low (below 0.5, especially in an image with low S/N ratio), you will effectively get a median filter. If you set the values high (greater than 2.0, especially in an image with high S/N ratio), you will effectively get a simple average filter. The key is to find the right balance of spurious pixel rejection and good S/N preservation. MultiCombine will correctly remove the pedestal from all images during the combine process. If you want to add a pedestal back into the final image for some reason (let me know if you come up with one), choose "Restore fixed pedestal" and enter a value in the "Pedestal value" text box. Click "Combine" when the settings are correct. The current open image in CCDSoft will be replaced with the results of the combine. File Contents ============= The MultiCombine setup routine installs three files onto your computer system: Name Location Description ---------------- ------------------------- ------------------- multiCombine.dll CCDSoft "Image Processing The plugin library Plugins" folder mscomctl.ocx c:\windows\system32 Control library (standard Windows controls, from Microsoft) ccrpftv6.ocx c:\windows\system32 Brad Martinez's FolderTreeview control Known Bugs ========== - I have not yet implemented any normalization functions, which are important when using median and trimmed mean combines. MultiCombine will probably not give good results when used to combine flats. - "Omit zero values" routine not yet implemented. - Has problems with large/many images. I don't have the ability to do wide-ranging testing of this issue, but I have noticed slowdowns when combining a large number of large images. I would appreciate any reports of problems that users experience. Please send problem reports to me at adam@usa.net, and include how many images you tried to combine, their dimensions, your operating system, and how much memory you have, if possible. You can quickly access your system info from within MultiCombine by clicking on the "About..." button from the main dialog box and then clicking the "System Info..." button. - MultiCombine cannot be run when a dummy image is not already loaded in CCDSoft. This is a vagary of how CCDSoft plugins work, and will most likely be fixed in an upcoming release of CCDSoft. Future Enhancements =================== - Automatically select mean trimming threshold - Carry over FITS header information, where appropriate - Post-combine hot and cold pixel removal - Combine summary information to help determine the trimming threshold (should allow better results than eyeballing the output) - Cycle through images in a folder before combining, and manually reject undesired images Version History =============== Version 0.5a: First public alpha Acknowledgements ================ Thanks to Software Bisque for an excellent application in CCDSoft, and to Matt Bisque for input on how CCDSoft works with plugins. Thanks to Russell Croman, author of the excellent SigmaReject plugin for MaximDL, for his writeup of the "sigma-reject" algorithm and suggestions on how to implement histogram normalization. Thanks to Ron Wodaski for inspiration and a kick in the ass. Thanks to the Spring 2003 class of the CCD Astro-Imaging camp for good ideas and enthusiasm. Copyright Information ===================== MultiCombine Plugin is copyright (c) 2003, Adam Forrest Block adam@usa.net http://www.mightyatom.com CCDSoft is copyright (c) 1992-2003 Software Bisque, Inc. and Santa Barbara Instruments Group. http://www.bisque.com http://www.sbig.com