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 09:51:35 -0700

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

Relevant Pages

  • Re: Sky Quality Meter
    ... I am using a 24 mm dia 18 mm fl lens that produces a 10 degree FOV ... The actually weighting with altitude would make the "effective altitude" closer to 60 degrees since the sensor response is lower at angles farther from the zenith. ...
    (sci.astro.amateur)
  • Re: Nikon D40 with 300mm lens AND teleconverter (Nikkor AF-S Teleconverter TC-20E II)
    ... by 1.5 to get the equivalent field of view, so the 18-55mm kit lens ... Greg with FoV. ... many of which will still refer to film SLRs and the focal lengths. ...
    (rec.photo.digital.slr-systems)
  • Re: Nikon D40 with 300mm lens AND teleconverter (Nikkor AF-S Teleconverter TC-20E II)
    ... by 1.5 to get the equivalent field of view, so the 18-55mm kit lens ... Greg with FoV. ... When dealing with DSLRs Greg will be buying lenses labelled, ...
    (rec.photo.digital.slr-systems)
  • Re: Full-frame or 1.5 DSLR?
    ... >>28mm lens provides the same usefulness on the 1Ds as it does on the 20D as ... Glad you don't think FOV is important, ... >length, max aperture, and usable area of focal plane. ... wide angle lenses than with telephotos, but I could imagine some long ...
    (rec.photo.digital.slr-systems)
  • Re: Can you recognise this starfield?
    ... This is why you should take good notes when observing, ... way it would help if you'd determine the FOV shown, ... For instance, "reasonably near zenith" doesn't help, since if this is a 1 ... And people always wonder why I keep a fairly detailed notebook of my ...
    (sci.astro.amateur)