Topic: Oh the Challenges of Recording Sunshine Duration

[EGR cooperative observer]

Hi Everyone -

One of the known limitations of sunshine duration sensors is not capturing the minutes shortly after sunrise and shortly before sunset.
Any ideas of an economical? way to have one camera pointing east and another west to record 1.5 hours after sunrise and 1.5 hours before sunset.

Perhaps I could use a PTZ camera and program it to point east in the morning and west in the afternoon.  I would record constantly for those 1.5 hours.

This would allow me (when I can't have a human observe every minute) to add at least a close estimate.

Thank you for your thoughts!

[mcrossley]

Sunshine hours requires a direct irradiation value of 120 W/m2, I doubt you will be getting that value close to sunrise/sunset.

[EGR cooperative observer]

Yeah, I've never agreed to the 120 standard.  A standard based on pre-historic Campbell Stokes.

The NWS, which I would concur with in this case, indicates that as long as a shadow is present, there is sun.  Their threshold is lower (closer to 85-90).

I agree on not getting that at sunrise / sunset.

[broadstairs]

The trouble with all the affordable solar sensors measure global radiation where the 120 w/m² does not apply. The ones which do measure direct radiation are way out of amateur price ranges.

Stuart

[davidmc36]

I am lucky enough to have acquired a Blake Larsen Sun Recorder at a sensible price.

A replacement will likely be out of my budget.

[EGR cooperative observer]

I will need to relocate my BL sunshine recorder as the National Weather Service will no longer be reporting the readings on it any more.

I have one alternative site picked out but it is at a high school football stadium and I'm wondering if the lights at night would be an issue?  Thoughts?

[PaulMy]

Hi,

I have one alternative site picked out but it is at a high school football stadium and I'm wondering if the lights at night would be an issue?  Thoughts?

I wouldn't think so.  The program will only record from sunrise to sunset. Mine wasn't close by a lighted field but there were street lights, and never had any issue.

Enjoy,
Paul

[Paulcheffus]

The trouble with all the affordable solar sensors measure global radiation where the 120 w/m² does not apply. The ones which do measure direct radiation are way out of amateur price ranges.

Stuart

Hi

I’ve used the formulas here for the global solar radiation sensor as a bit of an experiment to see what sort of figures I get.

https://docs.vaisala.com/r/M212407EN-R/en-US/GUID-FBAC10C6-3600-4046-8A37-8277A73E25C8/GUID-E0C5F208-D9BA-4A5A-A926-EF72DD47C8FB

Cheers

Paul

[davidmc36]

I found the calculation used by CMx was quite generous at declaring the sun was shining compare to the BL

[mcrossley]

I found the calculation used by CMx was quite generous at declaring the sun was shining compare to the BL

The calculation needs to be tuned to your location and sensor. The default calibration values are just a reasonable starter, with a bit of tuning it can become much more accurate.