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Again.. where does the 2 arcsec come from? The systematic difference between the two sets is 0.3 arcsec, not 2. The derived mean position is not much larger than the generally accepted uncertainty of catalogued data, whom do differ amongst themselves at the same order of magnitude... I did use only two bright reference stars and as Taichi mentioned the software selection mechanism does contribute a fair amount. That .fits image should have been sent long ago. My neuron channels are more than 2 arcsec off. .. Regards, Berto >>> Taichi Kato <tkato@kusastro.kyoto-u.ac.jp> 06/24/03 03:18AM >>> >> I generally don't consider 2arcsec as a "small systematic difference". >> ...high airmass...a more likely problem is differential refraction... What would be the expected amount of differential refraction at the Berto's airmass? This problem could be avoided using reference stars with similar colors to the object. The "hidden" problem of the software could be a more significant cause, though... We (naturally including Yamaoka-san) would be happy to receive FITS files (as usual) from Berto to make further astrometric analysis. The image would be also useful for web presentation for helping other observers' identification. In any case, a 2-arcsec accuracy of astrometry is hardly sufficient to confirm the identification in the LMC field! Regards, Taichi Kato -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. Mailscanner thanks transtec Computers for their support.
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