Starmap - Astronomy Apps for iPhone and iPad

The Tonight function of Starmap has been upgraded in version 3.0.

With one touch, Starmap users may discover in a single list all planets, meteor showers, stars, constellations and deep sky objects that can be observed at their location. This unique functionality is now enhanced with even more objects and filter options. A great help for beginners as well as for advanced night sky observers.

How it works.

	In Starmap, simply touch the icon Tonight from the bottom menu bar.
	Starmap PRO users will have access to the function in the Find section.
	iPad users will find the function in the bottom menu bar.

	Right away, Starmap computes the list of the celestial objects that can be seen tonight, for your exact GPS location and time of observation.The list includes: • planets • main stars • active shooting star regions • deep sky objects like nebulas and galaxies • remarkable double stars • constellations Given the large number of celestial objects in Starmap databases, the lists can be collapsed or filtered at your convenience. You can sort it easily by luminosity or by rise time.
	As the sky moves along the night due to the Earth rotation, celestial objects will not be visible all night long. Use the time slider or one of the presets for setting your exact period of observation.
	Starmap is a scientific tool made for casual star gazers  and advanced astronomers. Select your means of observation. Starmap will select the objects most suitable for you, from the most accessible for unaided eyed observation to the faintest objects that can only be observed through larger telescopes.

What’s behind.

Starmap computes instantly the position of about one thousand celestial bodies in less than 100 milliseconds on an iPhone 4. This does not only consist of single position in the sky but full trajectories over the time. The algorithm uses pre-computed time series and assemble them according to the user location and time of observation. Only objects located above a 15° imaginary horizon will be kept. Under this limit, the atmosphere generally hinders the observation.

This is a good example of how increased processing power in handheld devices provides new services to users, hidden behind a simple touch.
The same technique has been used for comets in Starmap. In the PRO and HD versions, the user has access to the list of comets sorted by identifiers but also by magnitude — meaning their luminosity. This implies the computation of 900 know comets, including their present position in space, their distance and their intensities, taking into account their albedo — a sort of whiteness factor.

This calculation is performed within 100 ms on a 3GS iPhone, and in 30ms on a iPhone 4.

For a programmer like me,  it is sometimes frustrating to encapsulate so many hours of work and optimized computing into a single touch. This makes the user’s life easier of course, and it is the purpose. With this post, I just wanted to spotlight that what appears as most natural requires generally a huge amount of work… especially for an application like Starmap. This makes the difference with other gadget planetarium applications :-)

 The sexy equations behinds Starmap … what users should never see …