WX CrA sequence (need/intercomparison)

(vsnet 668)

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


(vsnet 669)


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,


RASNZ designation

Return to HomePage