Deep Sky Logger

Deep Sky logger, DSL, is a work in progress and is not yet finished (it will be finished sometime in 2016!), here is a preview to get an taste of its features and what the end-product will look like. Also as I’m using parts of this site as an online CV here is some technical background:

  • DSL is aimed at the more serious astronomer, so it expects a certain level of knowledge, there are plenty of astronomy apps on the market this one’s USP is its tie in with this web site and the fact its aimed at the serious astronomer.
  • DSL will be free (although I may charge for the access to this site for centralising observations and images.)
  • The planets positions are accurate although I do interpolate the positions (using catmull-rom splines) in real-time when in OpenGL.
  • The system contains two simple SQLite databases, one containing information for all of the objects (nearly 80,000 rows), star charts, vector positions and so on. The second is the users database of observations and their equipment. This allows me to easily roll-out database updates and keep one copy of the bulk of the data on your android device, the user database is separate for each user, the star catalogue is shared. The schema’s have full referential integrity and are normalised to some extent, but for maintainability they are all still quite readable and efficient.
    DSL Main Schema

    DSL Main Schema

    DSL User Schema

    DSL User Schema

  • The star chart is rendered using OpenGL, so for example this reads each stars position from the SQLite database then renders it.
  • The data driving this site and the app are the same, I use some scripts to ensure I can us the same schema and SQL on this sites MySQL database and the apps SQLite database. You can see the interactive charts here, these images are rendered on the fly from the underling database in PHP.
  • The text on the star chart is also rendered (I have to do it by hand, GLUT isn’t yet ported to Android 🙁 ), although the font is Roboto it has been modified slightly to have extra characters added (greek alphabet and so on) and simplify rendering in OpenGL.
  • The background to the star chart is a texture mapped image of the milky way to provide a nice realistic backdrop, see the texture mapped sphere code here.
  • Images are fetched and cached using AQuery.
  • The app is fully themed to allow the user to toggle between normal screens and a red version to preserve dark adaptation, I’m aiming to improve to look and feel at a later date and will be using something like Holo Everywhere.
  • The ultimate aim is to link the data in DSL to this site so you can log on here to get a summary of all your observations, download PDF versions, etc. This will enable the site and the app to be linked to share information, this will be via a REST interface and whatever technologies work best, although I may have to chart for this version of the app (a pre version?) as I may need to up the spec of this site to cope with the extra load. But that’s for another day.

You may ask as to why the app is not release yet, there are 2 reasons. 1) its not finished and 2) its not slick enough yet, in particular the star chart needs some more work to use the android devices tilt sensors and so forth.

The main screen allows you to pick from one of the main deep sky observing catalogues. At the top you can also search for a specific object, view a star chart or see a list of tonight’s best objects, based on your observatories location. The progress bars give you an indication of what percentage of each catalogue you have seen so far (the 1 object observed so far for this user shows up as a slight blue edge on the left of the Messier Object below.


You can view all of the objects in each catalogue. Here you get a quick summary of the object, its type, brightness and name. If you have recorded an observation then you see a little green tick to the left indicating this.


You can click through to more information on a specific object. You also get an image which is fetched (and cached) from the NGC/IC Project (used by kind permission).


To record observations you need to tell the system about your equipment, this is done through the settings screen where you can enter your location, telescopes, eyepieces and so on. For each item you can choose a default which will be used when you record an observation.


Once the system knows about your kit you can record an observation:

Finally you can see a detailed star chart of each object so you can find it. This is rendered direct from the database using OpenGL. Planets, Constellations, Stars, Deep Sky Objects, Horizon, the Milky-Way, Ecliptic and much more are all rendered.


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