Star Selection

9 Apr 2011 16:28
Last Modified
13 Jan 2013 17:36

I wanted to be able to select individual stars for further information. In order to do fast lookups of stars near to a cursor or reticle I added a further spatial index to my background stars. Due to the inaccuracies of using right-ascension and declination near to the celestial poles, I used an indexing scheme based on cartesian coordinates. A screenshot is shown below in Figure 1.

Reticle for star selection

Figure 1. Reticle for star selection. Note that the reticle is shown at 2x scale for clarity.

More information on the star is shown after a configurable delay, and hidden when the reticle is no longer focussed on the object. This avoids rendering data when it is not required, and allows higher-latency data (such as from the internet) to be shown when ready. Going forward, I should consider a hierarchical indexing scheme such as a Hierarchical Triangular Mesh1, which would give me the ability to find the nearest star at a given level of resolution.

1 "Indexing the Sphere with the Hierarchical Triangular Mesh", Alexander S. Szalay, Jim Gray, George Fekete, Peter Z. Kunszt, Peter Kukol, and Ani Thakar, August 2005

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