[Kstars-devel] strategies for expanding the size of catalogs

[Jason Harris]

Hello,

One of the most popular complaints about KStars is that its catalogs are too 
small, and specifically that the star catalog doesn't go deep enough.

What would it take to include the HST Guide Star Catalog in KStars (about 15 
million stars, about 115 times the number now included)?  

Here's what I have in mind, I'd like to hear other thoughts on this:

We store all stars brighter than 6.0 (or some similar bright limit) in a 
single data file.  These objects are always loaded into memory when the 
program is running.

For fainter stars (6.0 to 15.0), the data files are split by region on the 
sky, so that we can dynamically load only those stars that are needed for the 
location that is currently being drawn.  In fact, the GSC is already split 
into 9537 regions.  This might be a good number of regions for us.

If we do this, then we're obviously going to be accessing the disk a lot while 
the program runs.  To keep the interface responsive, we can do things like:

* use binary data files to improve load times.

* sort each regional star data file by magnitude, so that we can stop reading 
the file when the zoom-dependent faint limit is reached.

* use "progressive drawing", where stars appear in the map as they are loaded, 
rather than waiting for the data stream before drawing the sky.  Obviously, 
we wouldn't draw each star as it's loaded, but for example whenever N 
thousand stars have been read, we can send them to the map.

* instead of keeping the GSC regions, we'd want our regions to conform to HTM 
triangles (though it's possible the GSC does use HTM for these regions...)

What do you think?  Is it a good idea to keep the brightest stars as a 
separate, non-regionalized catalog?  Will the progressive drawing work?

Obviously, the coding for this would wait until after the 4.0 release, but I 
wanted to put it on the list while I'm thinking about it.

thanks for any feedback,
Jason

-- 
KStars: KDE Desktop Planetarium
kstars at 30doradus.org