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(fwd) Re: to V or not to V - I couldn't resist it Date: Wed, 9 Jul 2003 10:02:49 +0200 (CEST) From: Ulisse Munari <munari@pd.astro.it> from A.Henden > I'll agree to this! Ground-based calibration is difficult at best. > But I'll extend it: some satellite should do spectrophotometry, > whether with grism or true spectroscopy, so that one has calibrated > spectra at reasonable resolution. Then you can make your own > standards-list for whatever filter system you want to use. GAIA > has promise if you are willing to wait a decade. Putting up a > 0.4m telescope, such as is proposed for Space Station, might be > sooner if they can be convinced to do spectroscopy rather than photometry. DIVA (the astrometric satellite recently cancelled by the German Space Agency from its program) was ment to obtained such type of low dispersion spectra (better to say energy distributions) running through the whole optical range, for all stars over the whole sky to a completness magnitude equivalent to V=15.5 for the mean K0 spectral type at this magnitude for field stars. That would have been a dream for photometrists, because band transmission profiles for known photometric systems could have been appplied to them and, viceversa, use them to reconstruct the profile of systems missing this piece of basic information. Virtually, it could have been possible to set up a full grid of reference stars for any old or new photometric system (which bands do not run outside the optical range), and link local to standard ones. Unfortunately DIVA, like the US counterpart FAME, will not fly. Ulisse
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