Re: [ATM] How far from the telescope should an artifical star beplaced

[Guy Brandenburg <gfbrandenburg@yahoo.com>]

I remember reading about this in one of the books put out by Willmann-Bell, possibly Suiter. It goes into detail on the size of the device, the distance, the f/ratio, and so on. At my house, it was essentially impossible to find any place that was far enough away because of all the trees we have. Or else, it's cloudy or rainy. Or it's dark. John Dobson, last week, when he visited our workshop, said that he used the insulators on telephone poles; a quarter mile was sufficient. He never bothered learning how to do the Foucault or Ronchi tests or any variations on that. He had a fairly easy way (for him) to tell what part of the mirror needed work based on where the out-of-focus lines were bright or dim, and depending on whether he was inside focus or outside focus. If I had had a diagram, it might have made more sense to me, but I couldn't quite follow it.
Guy

Kevin MIchael Zabbo <chaosopher23@yahoo.com> wrote:
How far away can you get the fake star? 30 feet? 100
yards? A mile? I guess that further away is better,
but if you have at your disposal two mountain tops,
you will still have to deal with atmospheric
turbulence from the valley below. A hundred feet is
probably sufficient.

Kevin of Eastern Iowa
Seeker of the Darkness

--- Bruce MacDonald 
wrote:

> G'Day all...
> "As far as necessary such that the rays of light
> from the pinpoint
> source are effectively parallel to each other when
> they encounter the
> objective mirror"
> 
> OK, how far is that?
> 
> Thanks,
> BM
> ________

Guy  Brandenburg
Washington, DC
My home page:
http://home.earthlink.net/~gfbranden/GFB_Home_Page.html
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