One of my PHP scripts will give you a good idea of what your ‘max’ UV should be for the current time with a clear sky based on your gps coordinates. Just change the ‘lat’ and ‘lon’ to match your location:
http://beentheresailedthat.com/ws/server/php/getUvByCoord.php?lat=40.65817&lon=-73.47492
From there, you can ‘guesstimate’ what it should be based on your current cloud cover.
–Sam
Thanks much for this.
I do suspect the UV is a bit high from the replacement Sky I received a couple weeks ago. Will compare when tempest arrives hopefully this week.
Thanks again !
Thanks Sam, here in Ohio showing a max of about 6 normally, although my Prod. Tempest is showing peaks of 7 to almost 8 today. Bit high still I think on Solar Radiation peaking today around a kilowatt/sq. m, I usually expect maybe 700-800 tops (unless some cloud edge defraction).
That PHP script is based on NOAA global observations, and compiled into a 1 degree database… Then extrapolated based on your local sunrise, sunset and solar noon, time of day… And day of month. And corrected for UV ‘float’ over the past 10 years.
In short… A bunch of voodoo magic.
If you’d like to see the reasoning, use getUvByCood_debug.php
–Sam
Lots of magic going on in that little white cylinder !
Lol. true.
I’ve been working on fine tuning this script for over a year…with help from a fellow WF supporter.
So awesome to have online peeps who work to invent and improve.
Looking at UV index again today. The script/formula matches the official weather statements (predicting index of 7 at this hour), but Sky is showing index of 10 at the moment. Avg daily max should be 7 for my city.
This is a new Sky unit received in the past few weeks as a replacement. Will have to compare with tempest whenever it arrives.
Dan your station seems to get shades around noon quite often. Calibration rejects each time since it is or to shady (cloudy day) or it goes up and down like a jojo
FAIL: no sufficiently clear days available during the analysis period.
Merci Eric. Yes the trees tend to cut the sun at around lunchtime. Obviously it’s not a problem during winter time though.
Thanks for clarifying. I wasn’t aware this is how calibration worked for Sky. When it arrives, my Tempest will have a clear catch of the sun (different location) so hopefully that will be ok. Note to self: UV index during summer is incorrect 
Thanks again Eric. Your help much appreciated for understanding how things work
If you can move the sky 1 or 2 days let’s say from 10 am to 2 pm in full sun (when it shines) most probably the cl will kick in. And since from there on it will most probably reject the following days for the same reason it doesn’t want to calibrate, it might stay ok
As an aside… I bet if somebody really wanted to compute the data over several months, they could reconstruct the virtual environment around somebody else’s Sky & Tempest units via UV & Wind. Would be an interesting (and probably complicated) project.
Yes I can do that. I’ll have to find my extra base somewhere in the house (the first is strongly fixed on an yard obelisk) but I’ll see what I can do. I’ll report back!
Thanks again for all your interventions in this community.
Experiment begun :). Moved Sky to new sunny location temporarily. Let’s see how it turns out over the next few days
Thanks again Eric.
I have seen UV values as high as 13 last week on my Sky unit, but I suppose that could be legitimate?
Depends where you are I suppose. I’m at latitude 46 (Northern Ontario) so my values are way too high for this area.
Looking forward to checking my revised results over the next few days as per Eric’s suggestions.
I’ll mod this in the next week to allow the user to choose a day/time to get the expected MAX UV values as well.
Right now it just returns the value for NOW.
–Sam
Thanks much. I hit UV 12.5 today with the uncalibrated Sky. Geez, I don’t think our northern plants and wildlife could survive with that kind of sun over here !
Hi,
I’ve been a bit suspicious of the values I’ve been getting for a while, but looking at it now they’re clearly wrong.
I’m getting a 5 moderate right now, in the middle of rain and grey skies, with the national weather showing <1 for the area. Is there anything that can be done to recalibrate it ? It’s regularly going up to 15, which for Ireland seems very unlikely.
Thanks
