sky quality meters and cloud sensors?????

[iwols]

hi all weve all been there but picture the scene.Not dark till late ,moon not quite up,not sure if there are thin clouds, not looking perfect,do i go for it? Which leads me on to how good are the sqm and cloud sensors,are they the same thing to some extent, 2 examples

https://www.firstlightoptics.com/unihedron-sky-quality-meters/unihedron-sqm-lu-dl-sky-quality-meter-with-usb-and-data-logging.html 

or the hitec astro usb weather cloud sensor   all comments suggestions appreciated

 

 

 

[discardedastro]

Cloud sensors and SQMs measure different things. Basically, your SQM measures visual brightness of the sky - your background noise, so to speak, for visual imaging. The cloud sensors, on the other hand, generally measure the temperature of the sky - the infrared brightness, effectively. This is because clouds reflect IR from the warm ground, and so warm skies are cloudy skies; you can relate sky warmth to cloud cover pretty accurately with a good sensor.

So cloud sensors tend to be used exclusively with automation or monitoring systems. If the clouds roll in, stop the session and close the observatory roof, that sort of thing.

SQMs on the other hand are telling you how good your skies look, assuming they're clear. So you generally need both if you want to do long-term monitoring (to let you discard the data with clouds in and average only over clear nights).

For a practical "is it worth setting everything up" answer, an SQM might be helpful but I'd put more faith in a weather app - all these things do is tell you about now!

Edited May 21, 2019 by discardedastro

[iwols]

thanks just wondered if the hitec also gave lower readings when it was still lightish,to some extent like the sqm's

[discardedastro]

The hitec won't show you how bright the background sky is if it's clear, no, or at least not appreciably I wouldn't have thought.