For many years occultation predictions have included information on 'known' double stars. This has 
been based on double stars documented on the Washington Double Star Catalog (WDS), and the 
Interferometric Catalogue - together with stars detected or suspected of being double as a result of 
lunar occultation observations.

There are significant problems associated with double stars 'discovered' in a lunar occultation. The 
most significant of these is that when an observer reported an observation as 'non-instantaneous' we 
have been too ready to 'interpret' the observation as being caused by a double star. Another issue 
is where a double star discovery/measurement should be documented. Clearly this should be the WDS or 
Interferometric catalog. However our past processes have generally not involved the WDS or 
Interferometric catalogs. As a result, the double star experts were largely ignorant of any 
discoveries made in occultations.

Over the last few weeks the issue of processing double star information has been the subject of some 
'behind the scenes' discussions involving certain key IOTA members and key personnel responsible for 
the WDS and the Interferometric catalogues. Key results from those discussions are:


* The WDS and Interferometric catalogue will be the determinative references for whether a star is a 
double star. Files such as 'XZDoubles Discoveries.dat' [used in occult and LOW], and 'dsFile' [used 
by USNO predictions, and before XZ80Q was created] will not constitute authority on whether or not a 
star is a double star.

* Where an observer records a lunar occultation, and there is clear evidence of the star being a 
double star, the process will involve a 'formal' documentation of the observation (such as a short, 
simple, paper in the Journal of Double Star Observations - possibly including a Limovie light 
curve). This will lead to the star being included in one or other of the WDS or Interferometric 
catalogues.

* where an observer records a lunar occultation that shows evidence that the star 'might' be a 
double star, that fact will be retained in the prediction system, with suitable alerts being 
included with predictions for that star.

These changes will provide a regime for properly treating non-instantaneous lunar occultation 
events. It will also ensure that lunar occultation discoveries are given proper credit and 
recognition outside of the occultation community.

The implementation of these changes will take a little time. There will need to be a review of all 
the 1100 OCC stars in the XZDoubles Discoveries file on several issues. David Dunham will also be 
reviewing those OCC stars that are currently entered in the Interferometric catalogue, to identify 
(and remove) those entries made with insufficient justification (which is suspected as being a large 
percentage.) And I will need to make some changes to the Occult program to provide appropriate 
messages with predictions. Accordingly the changes in the prediction system will not be implemented 
for several months. However we hope to have the new arrangements in place well before the start of 
2010.