This will start stuff growing...

[quanglewangle]

Good news. When the sun is out it's starting to get more intense.

We have been getting periods of photon flux density of over 500 μmol s^-1 m^-2 in last few days. Tomatoes and aubergines need 400 μmol s^-1 m^-2 just to get out of bed in the morning.

Mine have been hanging on but from now on I expect them to get going.

[Nicos]

I’ve noticed we’ve had a UV of 1 when the sun has been out. How does that relate to photon flux?

I can’t help but chuckle...all that comes to mind is a Delorian steaming away

[quanglewangle]

Nicos, UV of 1 what? What are the units?

[Nicos]

It just says Max UV Index 1 on the accuweather.com forecast - it goes up to 9 here at the night of summer

No idea about the units

[quanglewangle]

What follows contains sweeping assumptions. Be warned.

Noon summer sun reaches about 1500-1800 μmol s^-1 m^-2 so lets say your 9 is 1800 μmol s^-1 m^-2
That's about 200 μmol s^-1 m^-2 for each 1 on your scale.

200 μmol s^-1 m^-2 is not unreasonable for hazy winter sun.

I would expect on that basis for your reading to get to 2 at noon soon now with unobscured sun. If the sensor points straight up there is a cosine correction to apply to allow for the fact that the sun is quite low in the sky at the moment.

[Nicos]

OK...thanks - That helped me understand other links I read through .
I’ve never really looked into/ thought deeply about growlights or natural light particles per second per area before.
Interesting reading- thanks.

[quanglewangle]

Nicos, since you are interested here is a day's worth of sunshine data. This is today: mostly sunny with some fine weather cumulus.
Growing really only happens above 400 μmol s^-1 m^-2.
The big dip is shadow of a bush, which the sun will clear in a few weeks. The little dips are clouds.

[Nicos]

Gosh ,yes, that IS interesting to see!
Thanks for sharing.

[Snoop Puss]

I'm intrigued, QW. What are you using for your readings?

Anecdotal evidence here only: the weeds are sprouting and the grass is growing.

[quanglewangle]

^^^^
BH1715FVC light intensity sensor under hemispherical dome to effect some cosine correction. Connected to Raspberry pi running home brewed software. Backs off supplemental lights when sun is bright enough. (not often at present!)

Same setup, with temperature sensors, controls heat cables under greenhouse bed and propagater sand tray.

[Snoop Puss]

Sounds high tech stuff. I live off grid and don't have grow lights, not even a windowsill, in fact. Hope you have a great growing year, QW. Looks like you have everything you need to get off to a good start.

[quanglewangle]

Sun is nudging 600 s^-1 m^-2 .
Further up the thread I posted a daily graph from about a month a ago when sun was peaking just under 500 s^-1 m-^2.

Summer is coming