Olin Lathrop wrote:

> Stef Mientki wrote:
>
>> I agree, but it depends on what your goals are, and what is practical
>> realizable.
>> Our main goals are (some are just dreams for the moment ;-)
>> 1. show the major stars at the current location at the current time (In
>> Netherlands you cann't see too many stars ;-)
>> 2. show the moon and planets (maybe even some satalites)
>> 3. show the accelarated  movement of stars, moon and planets
>> 4. show the effect of light polution
>> 5. with some kind of pointer, point an area at the dome (I read
>> somewhere that LEDs can be used as light sensor, or the old PC-pen
>> trick), and the telescope outside moves to the selected area
>
>
> This sounds like a nice little project, and getting anything working 
> at all
> will give a lot of satifaction and learning.  Is there any reason you 
> need
> to project onto the inside of a hemisphere like a normal planetarium?  
> Why
> not redefine the star machine to be viewed from outside the sphere?

Maybe I wasn't clear enough, we are going to look outside onto the half 
sphere,
just like in the EyeBall. So projection is maybe the wrong word ???
But I think projecting gives a much better image, because of the 
radiation pattern of the LEDs.
If you look at a narrow beamed LED, you'll see a second radiation 
pattern, which is very widespread.
So the idea is to project the LEDs on the innerside of a 
semi-transparant sphere and have a better picture.
I just tested it with some semi-transparent white plexiglass (Litterary 
translated from Dutch we call this color "milkglass") and the effect is 
disappointing.
But if you just shine the LED through a piece of (white) paper, you get 
the widespread beam completely vanished, so that's what we really want. 
But how do we make a (strong enough) paper sphere, or is there some 
other coating which has the same effect  ??

> That
> would be a lot more achievable and novel.  After all the other way has 
> been
> done before.  You'll still have something cool to show off, perhaps even
> better.

Yes, IF we get it working,
and you what the problems are (6 copyrights?  ;-)

BTW, how many LEDs did you have to control in the EyeBall ?

cheers,
Stef

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