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Hello Bish-- >> It even seems to me that new errors are continously injected every time >> a new program or a version is released. It would unavoidable for >> every program to have some problems, but it sometimes looks like to me that >> CCD observers tend to preferrably or selectively use most unreliable software >> among various selections. X-) > > Every software is as reliable as each user can make it to be. > > Whenever one assumes blindly that all the softwares does what > one thinks they do, then the person is one step closer to shooting > his/her own feet. So don't assume that there is such a thing as > the "most unreliable" software. More often, many "software" problems > are due to user errors. > > In short, everyone should have some simple way to test and see if > your "software" works the way you expect it to be. If not, ask > developers about it. As one of the authors of AIP for Windows, I would like to comment on this point. When we wrote AIP for Windows, we designed the software to do only tasks that are appropriate for image processing software, that is, we extract the photometric information from CCD images as accurately as possible. Those tasks are to measure the sum of the image pixels in the stellar image, and to correctly subtract the sky background. We also copy information from the FITS header and write it into the output file. In other words, our goal was to convert the image data into tabular data with an absolute minimum of interference or interpretation. We also designed the program file output format to be easy to import into spreadsheet software such as Excel, or simple for a program in Basic to read. We assumed that users would wish to reduce their photometry in many different ways, and we wanted to make it easy for them to write custom routines. In other words, our philosophy is that image processing software should extract the photometric information from the image and pass along things like date and time exactly as they appear in the FITS header. Thus images are turned into raw information. But users always want software that does *more.* The only major concession we've made in this regard is to convert the FITS strings following the OBS_DATE and OBS_TIME keyords into Julian dates. Although it sounds simple, there are multiple FITS formats, and the camera manufacturers do not strictly adhere to the FITS standards. In addition, the computer's time and date stamps may be inaccurate, and the computer may or may not be set to UT. If any of these things are not done correctly, the Julian Day will be wrong. Users want the software to compute heliocentric correction. Users want the software to compute a V-star magnitude based on the magnitude of the C-star. If we did these things, key parts of the photometric reduction would occur out of sight and beyond the user's control, and there would be no way for the user to check the accuracy of the result. Therefore in AIP for Windows, we will *not* do these steps in the reduction -- these steps should be and must be the responsibility of the observer because they are important parts of the data reduction. To accomplish the next step, Lew Cook created an Excel templete that automatically reads AIP for Windows output files for sequences of images, does the reduction, compute JD, and plots the result. The reduction is transparent and open to the observer. This the observer can check and verify every step in the reduction, and thus CBA can be sure of getting good photometry. I would like to see other observers create spreadsheet templates and make them available to the community. --Richard Richard Berry AIP for Windows
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