Re: Sky Quality Meter

Yes, the FOV problem can be solved with a fast lens.
I am using a 24 mm dia 18 mm fl lens that produces a 10 degree FOV
and on another meter a lens that produces a 3 degree FOV.

The count rate remains near the level of a wide open detector.

Doug, did you calibrate this to Vj magnitude or measure sky brightness
with the cm500 and standard stars. It seems that between this meter and the one we are developing we have a new system, Si+Cm500, that will need
to be worked up in a peer review process.

I will do CM500 filtered CCD exposures of standard fields to calibrate
this system.
Have you done comparisons with Vj photometry ?

Dan


welch@xxxxxxxxxxxxxxxxxxx wrote: 
Tony,

The sensor is on the (front) side with the display (which is off during
measurement, of course!)

You are no doubt aware that there is a trade-off between total signal
and solid angle. Indeed the cone half-angle of 40 degrees will weight
the reading off the zenith,  but it is representative of a near-zenith
sky brightness. 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.

Cheers,
Doug Welch

.

Relevant Pages

  • Re: night sky meter project needs SX programmer
    ... a smaller FOV would be nice and I do operate the meter at zenith or to the north a bit. ... I will dig up a lens and give it a go. ... sky brightness doubles between 60 degrees and ...
    (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)