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Dear colleagues, Taichi Kato wrote: > So, my suggestion is to monthly get CCD photometry with a wide-field > camera. A weekly basis would be preferrable. With such equipment, > almost all bright Mira stars will have sufficient coverage to make > ephemerides. Of course, there is no neccesity for maximum predictions > for this type of observation, though... > > There was a good example of such coverage by the MISAO project a few > years ago. These observations reported to VSNET have illustrated the > ability of wide-field CCD survey to record such poorly observed LPVs. > The observations generally well agreed with visual observation with > respect to the maximum determination. The only problem is that the > time-consuming procedure for reporting by the MISAO project (or more > correctly, the human neccesity to examine PIXY output) has disabled further > reports. There must be a huge number of unreported, but meaningful, > measurements left in the hard disk of Yoshida-san's computer... it might > take a century for Yoshida-san to fully examine these results. > The reported inaccuracy of the PIXY will not be a significant problem > in determining these LPV light curves. The next step we would need is > the way to make PIXY more numerically reliable and automatic in producing > variable star reports. Implementation of a similar function in widely > available programs will naturally be also very welcomed. I guess those who want to operate such an activity will want to creat light curves and reveal the status by themselves. The reason why we the MISAO Project is now not operating such an observations is that Ken-ichi Kadota turned to concentrate on comet observations and stopped taking wide field images. Now we have wide field images of several nights. But they will not increase if none of our members will start taking wide field images again. The images are too few or too sparse to craete light curve on any star... That is the main reason why I stopped checking and reporting magntiude from our wide field images. BTW, observing many variable stars with wide field camera lens now requires checks by human before reporting the magnitude. That is a big problem. But the main reason of that is not because of the accuracy of the software. I do not know why the PIXY's results became so inaccurate in the case of Maciej's project. But in the case of the MISAO Project, it was not too inaccurate, as Taichi pointed out. Actually, I reported almost all data to VSNET, when I judged the star is O.K. I mean, the main problem in my case was not the accuracy, but whether the star is O.K. or not. The GCVS contains various kinds of stars. Many of them are good targets for your wide field camera lens. But many of them must be too faint. In those cases, the software often measures the magnitude of the neaby bright star as that of the faint variable. Then you have to delete them. Or, many of them become blending on wide field images. In those cases, the measured magnitude will be blended one. In the worst case, the software measures the magnitude of only the star when the image is sharp, but measures the blended magnitude when the image is not sharp. Then you have to delete them. I mean, the main problem is to select proper stars for your instruments. Maybe we have to select only poorly observed variable stars, too :-) The same problems occur on comparison stars. So maybe we also need a list of proper comparison stars, which will not become blended. Once a catalog of proper stars for your own style of observations, it will be easy to continue the observations of many variable stars with wide field camera lens, even using the PIXY System 2. I implemented PSF photometry to PIXY last week. So maybe the accuracy will be increased. The magnitude of TmzV868 were measured using the PSF photometry. In the case of the MISAO Project, there are some other reasons which caused difficulty. One is mixture of various focul lengths. A star became blended when using a focul length, but did not become blended when using another focul length... Another is that we mainly used 35-mm camera lens. But it was not good for photometry. One big problem was that most stars became blended. Another big problem was that it was too sharp. Most stars' light became one pixel, or two pixels on the images! Depending on the location, sometimes the light became on four pixels. It was extremely hard to measure the magnitude of those too sharp star images. So we should have used longer focul length. But using longer focul length, some stars, probably very red stars, became blur. We called it "infrared blur". Many LPV are very red and bright in infrared. So they may be blur on camera lens images. Then it is impossible to measure the magnitude precisely using any methods. Anyway, using your own list of variable stars, using the same instruments, taking images in proper intervals based on the type of your target stars, you will be obtain good results of many stars, I believe. Best regards, -- Seiichi Yoshida comet@aerith.net http://vsnet.aerith.net/
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