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(fwd) to V or not to V - I couldn't resist it From John Greaves: Well, The problems with regards to 'V' reportage are a bit endemic, throughout all levels of competence. One that used to annoy me with this 'CCD through an orange bit of glass problem', or CCDO as it seems to be more succinctly defined now, would be whenever Mr Liller found another new nova. He'd do follow up observations in time and quote a broadband V magnitude. And sometimes this broadband V magnitude would be directly quoted in the IAUC, even when Mr Marsden was still in charge, so it's not a new problem related to staffing changes. Sometimes the IAUC would actually quote it as V, without the 'broadband' word. So, it'd then be in the literature as a Johnson V measure, despite measuring greater flux and thus brighter than true Johnson. He actually uses an orange bit of glass. Not any old orange bit of glass, granted, but I know of no standard stars for schott and/or wratten number whatever it is. Maybe that's the answer? Talk Arne Henden into setting up some primary standards for kodak kaf chips and wratten orange filters ;) ? (I'll do the first star: Vega is O_kaf = 0.00). But whilst a skilled and respected and succesful nova hunting amateur, and an informed and IAU commission remitted professional body can be found making such errors of statement, it's not surprising the rest have trouble. (Oh, and in case this gets forwarded, emails read more evil than they are meant, often, so before acronimity gets thrown at me by folk imagining personal attacks upon their bestest friends, the above has happened and happens, it's an easy specific example to show, it's a problem, and it's wrong. However, I do not isolate it as being any worse or better than many other situations, it's just an easy one to show, as I say. The number of head in the sand, knee jerk attack, reactions I see in response to points of proper _scientific_ [ie methodological investigation] discussion fascinates me. Though it shouldn't suprise me really. Too much bleeding politicking and humbrage taking, not enough thought on what the point of the entire exercise is). The lust for photon count versus the desire for quality is quite common in the professional, multimillion USdollar astronomical field, too [we rarely suffer from multimillion anything in the UK, except the odd debt]. 'New' passbands get defined of ever broader bandwidths till they are almost useless for stars. 'That's because we're looking at galaxies primarily' is the answer sometimes, but really, quality return on investment would suggest that the information returned on all those stars incidentally included in the survey should be of better priority than given, and jigger the record book level limiting magnitudes' fetish. There should be a stromgren ubvy beta (beta's good for luminosity class determination) satellite up there, with a subexperiment in Wing photometry for the brighter red stuff onboard too. Maybe a blue-end subset too, as I don't think IUE went that faint, and was more spectroscopic, though that's probably not as necessary and/or visual. You can do quite a bit with Stroemgren c1, m1, beta and the various Wing indices. Information, not just data. Okay, a survey gives hints and reveals new things, and you follow up with better, more targeted, kit, at a later tim. But still. It's quite ironic really that several decades of space astronomy has led to the visual bands being the least well treated in some respects. The only 'global' visual band single experiment survey I can think of off hand only goes down to mag 8 ish, and that's in a unique and single colour passband (Hp). Even IRAS, though probably not of high definition, still carries 'multicolour' information. There's no visual 2MASS, for example. (Okay, there's ASAS, and also TASS in Tom D and Arne H and probably other incarnations, but all still a long way from finishing and the limiting magnitudes might only be 13 or so at the complete level). Ah well, I'm on the verge of descending into a rant. I'll leave it there. Maybe I ought to go and see if I can get a narrow passband orange bit of glass system together, and although it won't be Johnson, it won't be broadband V either. I'll call it dialup V I think. Cheers, and somewhat tongue in cheekily John John Greaves PS Combining the thoughts on set range orange filters and big survey use of broader passbands seemingly being acceptable, maybe some standard stars would be welcome. Whose going to pay for the survey though? Spectral response of CCD chips are documented enough, the commonest one gets picked and used both raw and orange filtered to set up a system, this giving a chance for O_ccd and R_ccd, so even colour information. So, lots of chips out there with different responses. Well, if you stick to the red sensitive ones there's always transformations. I believe there's only so many being used that aren't that markedly different. And such wouldn't be unprecedented either. The number of conversions the 2MASS usage guide carries between it and everybody elses K photometric system are enlightening as to the real world of photometry practice. Folk do what they can manage, which is rarely ideal. I believe the CBA people have done some work on transforming their kit's raw observations for use with standard system data, though whether they've done it by playing with numbers or common 'standard' stars, I don't know. I dunno, it's such a daft idea it might even be sensible. ;^)
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