I'm a Father to be of 250 Million!

Well, it's been a while since my last post. The kids had their spring break last week so I took some time off, but mostly I've been hunkered down in the trenches.

Detailing my slog with the stellar database might be about as interesting as reading about someone watching paint peel off the wall. But since this is what I've spent the majority of the last three years working on I should at least say something about it.

I didn't set out to redo the stellar database from scratch. I had a lot to build on as a starting point with the SkyTools 2 (ST2) database. But I get suckered into these things as I go along, slowly pulled ever deeper into the pit by the catalog monster. My primary goal was to include the full Washington Double Star (WDS) catalog. Simple enough. ST2 has many of the same pairs, but they are derived from the CCDM catalog. This has meant that the commonly used WDS identifiers haven't been present in the database, and that some pairs were simply missing. The thing is, the WDS has always been a huge mess! That's why I avoided it in the first place. Although much improved in recent years it is still rife with errors and mistakes. In addition to incorporating the WDS I needed to update to the latest General Catalog of Variable Stars (GCVS) and its accompanying New Suspected Variable (NSV) catalog.

I was also excited about the prospect of incorporating the USNO-A2.0 catalog to extend the database much fainter. I asked for and received permission to do this from Dave Monet.

But what really set things off was the publishing of the second version of the UCAC catalog. This catalog goes almost as faint as the old Guide Star Catalog (GSC) but with much improved data, including accurate proper motions. Throw in the new USNO-B1 catalog with stars and proper motions down very faint, and you have a lot of new data available.

So I set about incorporating all these catalogs into the ST2 database, in one way or another. The basic idea is to compile all the available data into the SkyTools database. That may seem straight forward, but I go about it in a very different way from other developers. Most astronomical software acts like a data engine, overlaying the data from various sources. But what I do is incorporate ahead of time all the available data into a custom database, and this includes double star components.

Take a WDS pair for instance. In fact, they may be two pairs that share the same primary star. One pair is close and the other distant. So we have the primary (A) star, with star B 2 arc seconds away at some position angle measured in 1902. In addition we have star C at a distance of 16 arc seconds and a position angle measured in 1991. The GCVS claims that the B component is variable. But the magnitude range of the variable star doesn't match the magnitude listed for the B component. So what's wrong? With the advent of these new stellar catalogs even the fainter stars have proper motions. The proper motions allow me to run the stars back in time to see how their relative positions have changed. I do this to find which USNO-B1 or UCAC2 star macthes each of the component stars. Then I run the stars back in time to 1991, and even 1902. And voila! Component C moves in close to the primary and star B moves farther away. The variable star referred to by the GCVS is actually star C, not star B. Only back in 1902 they were switched in position!

When you consider how many pairs there are in the WDS you might begin to understand the size of this detective work. Mostly I created programs that match the stars from various catalogs and solve these mysteries, but in many cases I needed to do the detective work by hand. So I created an interactive program and spent many hours matching stars, making thousands of my own corrections.

This sort of thing goes on and on as I match stars from all the catalogs, including HIPPARCOS, Tycho-2, GSC, UCAC2, USNO-A2.0, USNO-B1 and all the cross reference catalogs like the SAO, BD, and PPM.

I'm now at the point where it is all finally coming together in a final form. The stars with more than minimal data appear in my primary reference database. I fold the less interesting and/or fainter stars into the mix when the mapping databases are created. There are actually three of these databases, one that goes down to 7th magnitude, a second that goes to 10th, and a third that in the past went to 15+. With the addition of faint USNO-A2.0 stars, this latter database can now be optionally extended to magnitude 20.

So what does this all mean for the user? It means more double stars, more variable stars, more accurate positions, many more stars with colors and proper motions, and the possibility of a much larger stellar database to support imaging.

To take advantage of all this I'm adding two new tools to the charts. One will create rudimentary color-magnitude diagrams for stars within an area. The other will plot the proper motions of stars with small arrows. These tools should provide advanced users with the ability to judge for themselves whether or not a grouping of stars is a real cluster, or to investigate how the stars in a cluster move together over time.

But the most obvious change will be the size of the database. SkyTools 3 will be made available in two versions: "standard", and "professional" (the names may change later, but you get the idea). The new imaging features will be Incorporated into the pro version, along with an extended database. The pro version will ship on 2 DVDs. The number of stars available will jump from the current 18 million, to as many as 250 million!

Except in a few selected areas of the sky I've been using the standard database for testing because I can regenerate the 15th magnitude mapping databases in just a few minutes. I estimate that it will take 5 days running continuously to generate the final "pro" database! So I'm waiting until I have the stars debugged before I make the final run. But that time is coming; the SkyTools 3 pro database will very soon be born, and after all this work, I'm pretty excited about it!