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Hi collegues -observers,
As stated under the comments of my note 'Some Southern
RCBs /
June 96' which was sent to VSNET-OBS ,
WX CRA has no offical
sequences (yet!).
The WX CRA charts from the VSS of RASNZ give only lettered
comparison stars. Magnitude estimates by the method d(2)V(3)e
will eventually lead to properly derived magnitude values once the
lettered reference stars are calibrated. However this process could
take time and often lead to a dead end for observers (and/or their
observation results).
Some observers therefore tend to calibrate sequences themselves
and (impatient as they are) use them as such. This results in
systematic differences in observing records of those stars
between those observers. This should be avoided! Well, we all
know it but humans we are and we want to see figures!
The best we can do at present is to evaluate / quantify the
(im)precision of such a method. Actually I did compare my
sequences for WX CRA with those of 2 other observers and
found quite some differences (up to 0.5 magn) for some of them.
Therefore I propose to have an intercomparison to investigate our
abilities to derive sequences and I hereby invite Southern (and
others!) observers to take part in an intercomparison by sending
their estimates for the lettered stars on the RASNZ chart 381 for
WX CRA to VSNET under 'WX CRA intercomparison' or e-mail
them to myself at 'lagmonar@csir.co.za' if they prefer secrecy on
this matter.
Together with the calibrations, it is important to state how they
were obtained and how accurate you consider them (standard
uncertainty/one standard deviation/full certainty/95% confidence
level...just phrase it as you feel it).
It would be very interesting to have the participation of not only
visual observers but especially photo-electric photometrists (B
Sumner, Stan Walker... Southern Backyard Astronomers).
As I consider this matter important I will send this invitation on both VSNET-OBS and VSNET.
At this stage I do not know how popular this intercomparison will be, neither if there is much interest on this matter amongst observers. If things were to start moving I will follow this invitation up and send updates and ...dead lines. In case of a succesfull intercomparison, a full report will be produced in due course.
Best regards from Pretoria,
Berto Monard LagMonar@csir.co.za
Hi,
I received some interesting and encouraging responses so far on
this initiative. And indeed Northern observers are interested too
but they can't see so deep down under.
I could suggest they organise their own intercomparison, if they
have a need at all to determine non-existing sequences or rectify
discordant ones. We could organise something together?
As far the Southern sky is concerned, a lot is to be done and it
would be nice if we could sort something out. WX CRA is only a
beginning. Hopefully we will carry on.. and suggestions are
hereby welcomed.
I can think (off hand) on one discordant sequence on the V1830
SGR chart from the RASNZ. I discussed it allready with B Sumner.
It concerns a close by reference star just North of V1830. It's
given a magnitude of 12.0V. I have never seen it, even under
optimal conditions, and consider it to be well <12.5. VSNET (T.
Kato) gives a value of 12.55V for it which looks more likely to me.
What do you get?
As things progress I will keep you informed!
Best regards,
Berto
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