Lightmeter FAQ

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Q by TdG

1) first of all : can you provide me a (new ?) userid /password for your site ? I cannot access more with "Guest"/"IYA2009". ;-(

    I just checked with Guest it works. Maybe it was in use and Mediawiki
    does not handle double usage. Alternatively Gast and the same PW. But
    send me your favourite userID and I will setup your login with the
    same PW.

2) I'm starting with your lightmeter a large study program in Belgium (mobile version) At this time, I'm gathering information. But I will need to validate my calculation versus the most "suited" formulas set to gain : - lux - mag/arcsec²

   I thought a lot about how to express the results. I decided to recommend Watt per
   square-meter. Then the measurements are an exact extension of what meteorology
   measures as "total radiation" or "global radiation" during the day and into the
   I also discussed this with Jan Hollan following his "What is light poll." (link
   on the wiki, and he is OK with that.
   With the lightmeter we can directly calibrate to Sun and Moon, thus the astro-
   -stellar-reference is not necessary any more. The entire mag-system comes from problems
   to calibrate to other standards then Vega, we should not keep it outside astro-apps.
   Lux is problematic for many reasons, in particular with respect to the melatonin
   and LED-revolution issues. mag/arcsec² is an astronomical procedure, direction
   dependent more an emission measure and has no SI recognition and I see many problems as 
   we approach legislation. 

   Maybe we can discuss this on the phone +43 1 92 52 166 or next week in Tautenburg
   +49 36427 863 55 . Are you using skype or similar?

Which software version (on your site, when I will re-gain access ;-) is the most "accurate" today ? (with "capture" file saving, not only display)

  I prefer the linux-version because its OpenSource and you can modify it. The
  simple software for XP/NT/2000 provided by the manufacturer runs very robust
  and has a built-in reboot on error and continues after reboot
  if put into the AutoStart folder. The reboot feature was not necessary up to now
  for the Mark2.3.
  For production use the simple software

  with the download

  What serial number is your instrument? Could you put informations into
  the Lightmeter-list on the wiki?

What's the most suited set of formulas to use to compute this value from count, daylight, nir Marl2.3 captured values ?

  There are standard procedures on the wiki. Below the full-moon you can use a factor, e.g.
  5E-7 to Lux (for a factor 2 proxy, the exact value needs calibration) for the main sensor 
  and there is a manufacturer-recommended formula for the day- channels (both on wiki).
  I wrote a text and instruction for the calibration from Sun to Sirius-values but
  it requires some effort. The fastest way is to send me data from a view days
  and nights and I will do the calibration to the Sun and twilight.
  The daylight vis and nir sensors are only to help with a fast and rough calibration
  towards Lux to get an idea for correcting the non-linear daylight part. It is not
  high accuracy also for similar reasons than the SQM (and it actually uses a similar
  sensor, that has a non-lambertian characteristic and no hemispheric view). 

  The Mark 2.3 sensor are selected for their sensitivity so you can get a quick start
  by taking one of the existing calibrations for Mark 2.3. E.g for the Yonago or
  Lindenberg stations.
  Some calibrations are already on the GVO-Lightmeter-database (linked on the wiki) 
  and on the site pages. Note that Berlin, Linz, Vienna, KSO, Tautenburg etc  are Mark 2.2. The
  Lightmeter-List on the wiki gives you types and links to existin
10:42, 14. Apr. 2010 GuentherWuchterl

WH --GW (talk) 15:20, 28 April 2016 (CEST)