Solar projection telescope

I'm ordering lenses from Surplus Shed for my big solar projection scope.  The plan is a 150mm PNM objective lens with a 2600mm focal length, followed by a -800mm MNM lens spaced at 1890mm from it.  This should result in 202mm image of the sun approximately six meters away, for an effective focal length 23.1 meters!

I still don't know how I'll direct sunlight into the scope.  My first attempts will use a hard drive platter as a super-cheap mirror.

Open Star Map for Android

I've compiled and made minor changes to the Google Sky Map application.  In particular, on devices like the Kindle Fire without a compass, it won't go into the auto mode which tracks the sky.  On devices that do have a compass, it should still track, but if you turn off the tracking (lower left corner icon), it will remember that setting (Google set it not to remember the setting, because of users who couldn't figure it out).  You can download the apk for the newly named Open Star Map.

There are a lot of unsatisfactory things about Open Star Map.  For instance, the night mode doesn't change everything.  For another, the catalogs are shallow.

Google Sky Map now open source

Google has opened up Sky Map: announcement and source code.

Just built it with Eclipse. To build, download the source via svn. Then:

1. Import trunk/app as an existing-source Android 2.3.3 project.
2. In the Project Properties, go to Java Build Path and Libraries.
2.1. Press "Add JARs..." and select libGoogleAnalytics.jar from trunk/app/libs/libGoogleAnalytics.jar
2.2. Press "Add External JARs..." and select the two jars from trunk/tools/libs