Hi folks, talking to you over the interwebs is Valentin Boettcher who is overhauling the Deep Sky Object (DSO) system in the KStars Desktop Planetarium for the Google Summer of Code anno domini 2021.
This is the first post in a series and rather late in the coming, so let’s get right to it.
I’m currently studying for a master’s degree in physics at the TU-Dresden in, you’ve guessed it correctly, the beautiful city of Dresden (Germany). In Germany, we do have two study terms per year and the summer term usually coincides neatly with the GSOC so that I couldn’t participate in past years. This time around however, my schedule was finally sparse enough for me to have a go at it, and here we are :).
My first contact with KStars development was back in 2017 while I spent a year in New Zealand and had a lot of time at hand. My reasoning was, that I could learn mathematics and physics in UNI and should funnel my enthusiasm into familiarizing myself with software development and the open source software community. I promptly wiped my hackintosh laptop to put Linux with KDE on it1. After reading ESR’s famous “How To Become A Hacker”, I followed the advice given therein, which was to find an open source project and start hacking on it. I already liked KDE and space, so KStars was in the center of the Venn-diagram :P. I went ahead and busied myself with one of the junior jobs listed on the KStars web-site2. I quickly found that I liked figuring out how stuff in KStars worked and also got in contact with my mentor Jasem Mutlaq who was always available to answer questions and endure my barrage of instant messages on matrix :P. My second job was to draw comets a tail and learned that it is wise to do some code archaeology before going ahead and implementing functionality that is already present. From there on I contributed more or less regularly when I found the time in my semester breaks.
Now, finally, let’s talk a wee bit about the actual GSOC project. In KStars, everything that isn’t a Star or an object in our solar system, an asteroid, a satellite or a comet (I’m sure I forgot something) is a deep sky object (DSO). Prominent members of the DSO caste are galaxies (think M31, Andromeda), asterisms and nebulae. Of course there are a plethora of catalogs for specific types of DSOs (for example, Lynds Catalog of Dark Nebulae) as well as compilations like the New General Catalogue. The system for handling those catalogs in KStars has grown rather “organically” and is now a tangle between databases, CSV files and special case implementations. Many catalogs were mentioned explicitly in the code, making it hard to extend and generalize. Also, the sources of the catalogs and methods how they were transformed into the KStars format were inhomogeneous and hard to reproduce, making deduplication almost impossible. Finally, KStars just loaded all the DSOs into memory and computed their position on the virtual sky for every draw cycle, which made all too large catalogs infeasible. My task is now (and has been since the beginning of June) to implement a unified catalog format which can be loaded into a central database and supports deduplication. Furthermore, taking inspiration from the handling of star catalogs in KStars, the objects should be trixel3indexed and cached in and out of memory (but only for large catalogs). Finally, it would be very desirable to make the creation/compilation of the catalogs reproducible and easily extendable to facilitate future maintenance.
This sounds like a big heap of stuff to get done and in the next post I will be detailing how it’s going so far :).
Cheers, Valentin
Assigning each object to a trixel makes it efficient to retrieve all objects from a certain part of the sky.
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