[vsnet-survey 47] !re Re: ROSAT PSPC updated!

[no name <crawl@zoom.co.uk>]

re: survey 46...

> Rejections seem to have preferably done in well-known systems ;-)
> I have found another, V616 Mon = A0620-00. Black hole researchers
> should be careful in using 2RXP.

&

> 1RXP:
> 
> 062244.7 -002054 (2000.0) 1RXPJ062244-0020.9 0.0011 0.89 -0.06
> 
> 2RXP:
> 
> None?!

The actual result for 2RXP is:

          2RXPJ062244.7+002045

A whole plethora of 1RXP objects surround V616 Mon at -0 degrees
declinations...

...a whole plethora of 2RXP objects lie directly above these at +0
degress declinations!

The 2RXP is put together by different working teams.  The above 2RXP
cluster are credited to a US group.  Further to the west I found other
examples in the +/- 0 degree declination range, on the edge of the
Rossette Nebula.  These were credited to the MPE Garching [Germany]
group.

Thus it seems that the errors have been made during the processing to
the final catalogue format throughout the +/- zero degree zone [small
sample investigated only!].

Interestingly, the decimal degree entries in the catalogue are also in
error with respect to sign, which shows that the sexigesimal positions
probably precede the decimal ones.

This is an old problem caused by astronomy using a sexigesimal system
with a zero point equator [interestingly UCAC1 uses "south polar
distance" to avoid this], and computers not having a character for -0. 
A similar one exists due the lack of a null character in computers: eg
is such and such a star really B-V 0.00, or was that entry empty, but
filled with 0 on subsequent processing!  That's why we often see "99.99"
a lot in datasets.

I'm going to assume that this error is global around the entire
celestial equator: it is probably best to allow for it in investigations
using 2RXP [ie cover both sides of 0], though logically it should only
be -0 declinations that suffer.

I've looked at the "anti-position" of V518 Per and no 2RXP object occurs
there, so it is probably not some perverse global inversion of the
heavens!

John

[PS is the eclipse as dark as it looks on some of the webcams? ;) ]

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