Re: night sky meter project needs SX programmer

From: Dan McKenna (mckenna_at_as.arizona.edu)
Date: 07/08/04 

Date: Thu, 08 Jul 2004 10:56:26 -0700

Tony,

I think that my last last post was in error.
A 57 mm fl will give you assuming a 1 mm detector a 1 degree fov not 57 deg!
so for a 0.1 rad fov we require a fl of 10 mm this would be a f 1 lens or faster
to meet my needs.

I don't have a 1 cm f1 lens to try.

Maybe a plastic asphere ?

Or do I still have it wrong ?

Dan

Dan McKenna wrote:

> Hi Tony,
>
> Yes, a smaller FOV would be nice and I do operate the meter at zenith or to the north a bit.
> The present part, TSL230, is in a clear dip package with the photo diode about 1 mm
> from the surface. The photo diode array (8 by 8) is about .93 mm on a side.
>
> For a fov of 0.1 rad (~5.7 deg) we need a focal length of about 530 mm
> now the light on the detector due to sky area is 1% of the 1 rad fov and so we need
> 10 times the area of the photo diode and so we need a 1 cm dia lens
>
> Seems like it would be easy to do although some one my get shot pointing around
> a 530 mm tube.
>
> Is that correct ?
>
> Ok then, I will dig up a lens and give it a go.
>
> I am now waiting for samples of the TSL237 that claims to have better dark properties
> and higher sensitivity. This device has a dome lens on the package.
>
> Dan
>
> Tony Flanders wrote:
>
> > Dan McKenna <mckenna@as.arizona.edu> wrote in message news:<40EC6BAC.9809BA10@as.arizona.edu>...
> >
> > > The detector that measures the light level is filtered by hoya
> > > CM 500 glass and has a simple field stop to limit the field of
> > > view to about 1 Radian (57.3 or so degrees)
> >
> > It would be nice to have the option of fitting it with a fast
> > lens (doesn't have to be fancy, could even be a singlet) to
> > get a narrower FOV without unduly restricting the incoming light.
> > One radian is fine for zenith measurements but not great for
> > anything else. At a typical suburban site, facing toward the
> > city center, sky brightness doubles between 60 degrees and
> > 30 degrees above the horizon, and doubles again at 15 degrees.
> > That means that a 1-radian bucket is catching a wide range
> > of sky brightnesses unless pointed almost directly upward.
> >
> > - Tony Flanders

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