Lightmeter FAQ
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 twilight.
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
http://kuffner-sternwarte.at/hms/wiki/index.php5?title=Lightmeter-Driver#Windows_XP.2FNT.2F2000
with the download
http://kuffner-sternwarte.at/hms/wiki/uploads/Lightmeter.zip
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