I've just downloaded, decompressed and run catgen on the PPMXL catalog data using catgen according to the instructions here:
http://www.ap-i.net/skychart/en/news/ppmxl_catalog
(Be warned if you're going to do the same downloading the catalog you need about 40GB of Internet download and 234 GB of disk (though you can bring this down to 156GB if you compress the right directories ahead of time. That's GB not MB. Don't even attempt this unless you've got a decent Internet plan and plenty of disk space to spare)
Got about 127kb worth of rejects out of catgen, but when you're talking 900 million stars that's nothing I was worried about and I don't think the data is corrupt. (PPMXL attempts to be complete to magnitude 20)
Within the first few minutes of playing I stumbled on the pattern in the attached images. I have no idea whether this pattern is a real phenomenon, or some strange artifact of the way the catalog has been created, or some sort of strangeness in the import. Playing around with DSS images, Skyview, and SIMBAD hasn't helped. There is a really bright object in the field as you can see, but that's about as much as I've been able to work out in the hour or so I've had to play. (I only dabble in Astronomy these days so I'm slow to do anything). Anyone else have any answers or know how I'd go about working this out?
