Environment setting using OpenWeatherMap


#1

When I set this option in SGP, the reading for “Cloud Cover” seems to be completely wrong. Specifically, when the sky was completely overcast, the Cloud Cover was stated to be “0%”. Now the reading is 12%, and there is not much sign of any clear sky.
Is it possible that the reading is “back to front”, i.e. that 0% cloud cover means overcast, and 100% cloud cover means clear?

If so, is the mistake in SGP or in the OpenWeatherMap data?

I also note that the values for seeing and sky brightness are both “NA”, which would make sense for a cloudy condition.

Stephen Avery


#2

If this is an error it would be in the ASCOM driver for OpenWeather and not SGPro. SGPro just reads the data and throws it on the screen. It is likely that neither app has a bug though… the accuracy of any global weather service is questionable at best.


#3

Dear Ken,

Thanks for your comment. Whilst accepting that SGPro just takes the data and displays it, is it possible that the data is being wrongly interpreted? In other words, data meaning say 15% cloud is being interpreted as 15% clear, or vice versa?

Best regards,

Stephen
Stephen Avery
Wilding Farm Cottage
Cinder Hill
Chailey
East Sussex, BN8 4HP


#4

Hi Stephen,

I sometimes use the OpenWeatherMap data on the OBS computer when I have it connected to the internet. I have never noticed a problem. Having said that it may not be 100% accurate because I am 20 km away from the actual WeatherMap station that I am monitoring. Have you checked online what the station you have chosen is actually transmitting for cloud cover etc. It would be easy, any time of day to check that against your actual skies.
Right now my local station is showing cloud cover 92%, but as I look up, I would say it is more like 60% max.

Brendan.


#5

Dear Brendan,

Thanks for your input.

I am based in Chailey, East Sussex, UK. The nearest weather station is located in Newick, which is only about 3 km away. I am also about 10 km from the towns of Lewes and Haywards Heath. When entering these three place names into the weather locator on the site, each gives me a cloud cover reading of 36%, at this is indeed what the API in SGPro is giving too.

However, when I look out of the window, I would estimate the cloud cover to be at least 90%! Perhaps the weather stations are only looking at low-level cloud, and not the total cloud thickness, which is important for astrophotography.

Conclusion - OpenWeatherMap is not much help for Astrophotography!

Best regards,

Stephen

Stephen Avery
Wilding Farm Cottage
Cinder Hill
Chailey
East Sussex, BN8 4HP


#6

Yes Stephen - agree 100%. If you want a weather station for accurate input…whether for safety or just to record the data on the FITS - I am afraid you will have to have a local monitor installed. For temperature and humidity I use BlueAstro Stickstation. For cloud cover (and wind/rain I suppose), I rely on Mark1 eyeball :slight_smile:

Brendan


#7

There is not:

http://www.ascom-standards.org/Help/Developer/html/P_ASCOM_DriverAccess_ObservingConditions_CloudCover.htm


#8

Ken,

Thanks for your further explanation.

I checked the Cloud Cover percentage again this evening and it now says 92%, and indeed the sky is very cloudy, so perhaps something has changed! Last night, a similar sky condition was given as 0%.

Thanks for bringing this source of weather information to my attention and for implementing it in SGP.

All the best,

Stephen Avery


www.mainsequencesoftware.com