Return to Home Page
Arne, I consider 0.3 arcsec (not 2 as you state) small but not unsignificant although differential refraction alone may be fully responsible for it in these circumstances. As I anticipated in an earlier posting... BTW the positional difference with published data of the indicated star is also of the same order... Regards, Berto >>> Arne Henden <aah@nofs.navy.mil> 06/23/03 08:59PM >>> I generally don't consider 2arcsec as a "small systematic difference". I think you are working at high airmass since you get both evening and morning observations, so a more likely problem is differential refraction in your field, especially if you are taking unfiltered exposures. If these were unfiltered observations, you should consider using a filter or two to narrow your bandpass (they have other uses than just to provide standardized photometry!). Arne Berto Monard wrote: > The following astrometric positions for the new variable were derived on images taken during early evening and pre-dawn. The scattering is indicated by error limits: the actual error incl systematic off-sets of the Tycho reference stars are not included and are estimated to be much larger: > > 2 morning sets: 05 08 25.56 +/ 0.03 -68 26 22.3 +/- 0.0 > 1 evening set: 05 08 25.92 -68 26 22.7 > > There seems to be a small systematic difference in RA between the sets taken about 12h apart. > > Considering the overall astrometric uncertainty, the derived positions coincide well with that of the earlier identified star. > > I'll do one more evening measurement when clouds stay away. > > Regards, > > Berto Monard > Bronberg Observatory / CBA Pretoria > > -- 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.
Return to the Powerful Daisaku
vsnet-adm@kusastro.kyoto-u.ac.jp
