M. Adam Davis wrote:

>On 9/7/05, Stef Mientki <s.mientki@mailbox.kun.nl> wrote:
>  
>
>>Yes you're right.
>>I just did some tests with medium bright LEDs at 100 mA (goal is bright
>>LEDs at 200 mA),
>>and 5Hz is too low, 20 Hz seems to be a good compromise.
>>So the 1 degree equivalence is 125 usec.
>>Even with this "low" current and medium bright LEDs, 10us pulses (for
>>the weakest stars) seems to be just bright enough.
>>    
>>
>
>Have you considered a laser scanner assembly pointing into a fisheye
>lens?  You can cover the entire dome with a few lasers, some optics,
>and a fast scanner. 
>
well laser projection crossed my mind,
but as my son (age 14) should do the job (and hopefully learn something 
from it),
I guess laser projection is far too difficult.

> Would probably be less work, and perhaps cheaper,
>than a spinning assembly of hundreds of LEDs.  Much less noise as
>well.
>
Yes, except I doubt if it is cheaper,
I estimate that the total material costs are below Euro 100 (I'm always 
an optimist ;-)
Another disadvantage (but I'm not an expert), the cheap lasers are red 
or green,
and stars are white :-(

>  Take off the translucent dome and the stars appear on the
>ceiling.
>  
>
Yes that would be realy great !
triggered by you idea I just found this website:
  http://www.es.com/products/digital_theater/digistar3-laser.asp

thanks,
Stef Mientki

>-Adam
>
>  
>
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