[ATM] Calibration Ideas for Dark Sky Meter (aDSM)

["Jim Miller" <jim@jtmiller.com>]

Hi All

I'm looking for "absolute" calibration ideas for my absolute Dark Sky Meter
(aDSM). My current idea is to use Vega at zenith on a "clear" night to give
me a mag0 reading. Looking at Cart du Ceil at the area around Vega with a 1°
FOV shows only a few relatively dim stars which should contribute to a
calibration inaccuracy well below the measurement precision of this
instrument. In operation one would point to Vega on a suitable occasion,
press the calibration button and the unit would establish that as Magnitude
0. All other measurements would ratiometrically derive from that stored
value.

Others have suggested several potential problems with this approach
including clouds, haze, unsuitability of Vega at other lattitudes and times
of year.

The problem with artificial sources that I can see so far is that it is
difficult to get their magnitude and color temp down to starlike levels so
as to remain within the dynamic range of this device. If anyone has some
ideas for obtaining a suitable artificial source I'd be grateful.

As far as the electonic part of the design that's coming along pretty good.
I'll post a schematic and parts list on my website (www.jtmiller.com) in the
next week for anyone who's interested. I'm planning to build three units
initially to compare the results among them. Then I'd like to send two of
the units to interested parties who could try them out.

The goal is to have anyone with the requisite technical skills to be able to
buy the parts and build one.

jtm

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