Hi Stefano

"I made the changes you suggested: no results.
It is always the same."

Well, it seems it was all to do with a new new feature, so yes I was giving you lots of red herrings after all!

Ah well, Bill's sorted it now it seems.


I'll kind of say one general thing to everybody. Bill seems to be in the heart of doing lots of new features which I think he's said in the past on this list may well be part of the ongoing Guide 9 development.

On the other hand data sources are in a state of flux, and seem to be changing arbitrarily, as well as increasingly new ones being available online, yet still not having finished mapping the entire sky, and often these are not catalogued or provided to any global standard, despite what we all hear about VO.

Fortunately Bill always provides these free downloadable upgrades of the "engine" of Guide online.

But we'll all have to keep in mind that no matter how perfect Guide 9 ends up being, bits of it'll still get broken at times because these data sources and webservices are either going to be in a state of flux over the next few years, or simply just not done properly to any standard. Lists exist with either no coordinates given or badly quoted coordinates, you're supposed to look them up by name in SIMBAD or something, which is fine for those that don't want to plot them up graphically on a map.

If the CDS at Strasbourg didn't exist and have a data tradition, data would likely only be available in VOTable and .csv format. Sorted ascii fixed length column files and probably sorted FITS files are the easiest and fastest to read and plot up, especially when big. CDS provides those. Comma delimited files are rarely sortable (if only because numbers rarely have the preceding padding zeroes in that format), and large datastets can be sorted, but often aren't, as database engines don't necessarily need that. UCAC3 is usable, and Bill looks to have adapted Guide for it, but he had to treat it as a special case. For big datasets this might become the norm. Especially as nowadays people are quite happy to copy full catalogues of many gigabytes size to their hard disk. But these catalogues are often provided in nonstandard, unique, formats, for ease of distribution (source UCAC3 is compressed in a special way to fit on the DVD, using a homegrown directly readable compression rather than any proprietary/commercial compression).

Although before long it might be possible for a lot of people to use datafiles remotely, over the web, instead of having catalogues on hard disk, it's interesting that people still seem to prefer to have the big source catalogues on hard disk, even when it isn't a matter that they're using a laptop at a remote observing site.

Cheers

John