Star autoguide with RPi - (2) Artificial star for software testing

The first problem come to me is how do I test my software.  I need a small bright spot act as star.  First, what I did is holding a flashlight and create a pinhole with may hand.  Of course, the room light has been turned off.  This method work for two days, but it is really annoying.  Because the room light need to be turn on and off, and the star light intensity, size and position are not stable.

Therefore, I have invented another 'clever' method.  Use a piece of black paper with white dots.  It fails at the first few trials, then I give it up.

So, I decide to create a artificial star by using optical method.  The end product looks like a big funny looking gun, and it works very well!!  :)

Here is how I build the artificial star for testing my software.  First, Find a lens (my lens has 16" focal length) and PVC pipe.  Below is just a empty tube with a lens insider.  Lens to the end of tube (black PVC) is about 16" apart.  Total cost ~$15.

Just a lens inside of tube, nothing else.

Make many (>20) pinholes on a sheet of aluminum foil. within 1" diameter area.  If possible, try to make those holes as small as possible.

Attach it to the end of reversed telescope tube.  And then put it aside for now.

Webcam modification.  I just pick a random bullet shape webcam for this application.  If you know any camera sensor with higher sensitivity, use it.  Below webcam cost ~$10 for a new one.

Remove front cover and lenses.  If you know how to remove IR block filter, remove it for better light sensitivity.   Wrap paper around the camera for better fitting into guide scope. 

Insert the webcam into guide scope.

Wrap paper around the tip of guide scope too for better fitting to artificial star generator.

Next, adjust focus...

Done!  The webcam can pick up 'star' from ambient light through pinholes.  Just point it to a wall, and the many 'star' images already saturated.  The result is much better then expected.