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Re: Software problem in time-series photometry > I don't think the C-offset is the default in AIP4WIN. > > The default setting for C tracking will IMO be able to process timeseries > taken in altaz. It will even allow to hook V or K on a moving comet on the > images to do photometry on it. Yes, constant C-offset (in X,Y coordinates) will not work for an Alt-Az mount. However, if there is an option for "trianglution" to determine the V position, it will work nice. When constant C-offset is appicable with your instrument, I will by all means recommend to use this option. > The problem with the default setting is that the C selection/centering is > quite nervous as if the aperture wants to jump away from the selected C > star. I have also heard from some of our observers that they sometimes find a difficulty in centering on the first image. Such a "jump" is unexpected if the centroid is contained the initially given aperture. If the same centering algorithm is used in actual aperture photometry, this may give a hint for the explanation of the observed photometric behavior (as stated in my initial posting). > Multiple image photometry in manual mode (pe for faint stars) is not working > well and therefore not accurate and time consuming. If I remember well, it > doesn't work in C-offset at all.. I mean by "manual measurements" make manual aperture photometry by applying manual aperture and by manually centering on the object. No automatic process is (intentionally) involved. Yes, this is time-consuming and need experience, but when automatic photometry seems to give unrealistic data, one should always return to this "manual mode" to see what could be wrong. Most frequently, one would find that the automatic software does not behave as intended. Regards, Taichi Kato
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