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swag72

Cloud sensors - What are the benefits?

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Sorry if this is in the wrong part of the forum, just couldn't decide where it should go!! :smiley:

Cloud sensors - What are people's thoughts on these and why do you use them? How does it help your astronomy? Why are they so expensive and why does everything in astronomy assume that you have some DIY / electronics / soldering iron capabilities. For someone who has none of the above, it looks like even the most basic of these will cost in excess of £250 :eek:

At that price, is it something that is even worth considering? I can look in the sky and see if it's cloudy - What would I achieve with one?

Looking forward to your replies on this one - There's always bits and pieces I like looking at!!!

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They're good if you want to start automating your set-up. For example, with a cloud sensor (and rain sensor, they usually include that too), you could start an imaging run, go to bed and have the software close the telescope down when the clouds come in. That also needs a fair bit more hardware/software of course.

Some models have a simpilier solution, where they have an alarm you can take with you, which the cloud sensor will activate when it detects cloudy/clear sky (depending on set-up). So, you can take the alarm to bed and get woken up when it's clear/cloudy. Whether that is appealing is a personal choice :)

If you're happy being an 'engaged' observer (i.e. you like to stay awake while you're observing), I don't see much point in having one.

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I don't want automation and only wanted to see if there was a nice simple example out there that would just be able to put some figures to the night, so to speak. It looks clear, but is it clearer than the night before for example? Just some thoughts from a simpleton!!

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One of the reasons that people (who talk about cloud sensors) include some electronics / DIY skills is because they are so expensive to buy.

My cloud sensor (OK, it's still just a circuit board with an LCD readout) was about £30 of parts and as you observe, they cost several hundred ££s to buy. That's my sort of incentive! In essence all it consists of is a non-contact thermometer sensor, a microprocessor to get the readings and a display to see what the differential is between sky temperature and ambient temperature. The DIY approach lets people add other features: an alarm as mentioned, a PC interface to let you compare conditions against past cloudiness (and provide some quantitative comparison with sky conditions) or maybe some other abilities, too.

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....... That's my sort of incentive! ......

My sort of incentive is one that doesn't involve any building or making on my part. It's just not my bag. Shame that for those of us who are not DIY / electronics minded we are shafted for the priviledge by companies that make this stuff.

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I have ordered a AAG cloudwatcher.

At the end i want to have my setup working remotely, but for now i want to use it to detect clouds and rain.

My setup is already working remotely, everything is in the back garden, i get the scope cover of the setup, sync the sky x and then i am off.

all the controls are done from inside my home, so the AAG cloudwatcher is the only thing i need yet to keep an eye out.

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My sort of incentive is one that doesn't involve any building or making on my part. It's just not my bag. Shame that for those of us who are not DIY / electronics minded we are shafted for the priviledge by companies that make this stuff.

i have a home made one but dont use it at the moment as most times here i can tell if it is going to be dry by looking at the satellite pics on the web.

It does show up fine cloud quite well as well, my cloud sensor that is.

Commercial ones are expensive as a lot of work goes into the software and it all has to be tested...plus they are not selling large quantities it is the astro community after all.

I dont think you are being shafted as such.

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How do cloud sensors work?
When the sky is clear, the air that the sensor can "see" is quite cold - minus several 10's °C. Clouds however, are relatively warm. So a cloud sensor contains a device that measures the temperature of the sky it's pointed at: cold == clear, warm == cloudy.

In theory, you could use an IR non-contact thermometer. The drawback is that you'd then have to go outside, aim it at the sky and take a reading. If you have to do that, you might as well just look at the sky yourself ;). So most cloud sensors are mechanically designed to sit outside in all weathers, not break, prevent water ingress and (ideally) to not frost over in the winter. They also have features that either allow control of an electrically operated dome; to roll it closed if it gets cloudy, an alarm to alert the owner to a clear sky (or incoming cloud) and possibly a PC interface for us nerdy types who like collecting data.

Edited by pete_l

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The AAG_CloudWatcher has proven itself to be a must-have addition to my battery of observatory sensors. Once the parameters have been configured correctly for the site at which the device is being used it is amazingly accurate. It's nice to be able to become engrossed in something inside while knowing that nothing can sneak up on me, and even nicer to be able to see what's going on atop the mountain while I'm down in the valley.

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I've been running one for about a year and have been very impressed with how reliable it's been. It does seem like the cloud/clear level is different in winter/summer (not surprising, as it's a difference in temperatures) -- have others found that? The rain gauge doesn't seem quite as sensitive as I'd hoped, but picks up all but the lightest rain.

Overall very impressed with it. We're planning to link it in with an automated system this summer.

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It does seem like the cloud/clear level is different in winter/summer (not surprising, as it's a difference in temperatures) -- have others found that?

Yes. The "default" setting was not ideal for my site (high alpine, very cold), but once adjusted to the config as suggested in the manual it's been bang on ever since. But there is a definite variation from season to season, although not enough for me to bother with fiddling with the settings any more.

The rain gauge doesn't seem quite as sensitive as I'd hoped, but picks up all but the lightest rain.

I've found it to be particularly sensitive to dew, ice and snow, which is good. My site doesn't receive much rain, so I can live with less sensitivity there, although I have to say I haven't noticed any problems.

Overall very impressed with it.

Same. I was concerned that it may have been a bit gimmicky and ineffective, but now I wouldn't be without it. Well worth the money, in my opinion.

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@ FraserClarke - Which clouds sensors are you using? Would be interetsed to know :smiley:

The AAG one looks good.

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@ FraserClarke - Which clouds sensors are you using? Would be interetsed to know :smiley:

The AAG one looks good.

Auroratech Cloud Sensor;

http://www.auroraeurotech.com/CloudSensor.php

But looking at the hardware, it looks the same as the AAG one... Software looks very similar too, so I suspect they might be pretty similar and just rebadged a bit.

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Auroratech Cloud Sensor;

http://www.auroraeurotech.com/CloudSensor.php

But looking at the hardware, it looks the same as the AAG one... Software looks very similar too, so I suspect they might be pretty similar and just rebadged a bit.

They all seem to use melexis 90614 type ir sensors and the rest of the hardware looks pretty much the same as well.

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Resurrecting the thread as I'm looking to invest in one & it came up in googles..

I was wondering if the opinions are still the same some 18 months on. I'm leaning towards the Aurora as the AAG seems to be half as much again & I don't see much difference?

Or are there other products out there now I've not yet found?

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The AAG works just fine. Software is good as is the ACP and CCD Autopilot integration.

/per

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Beware of the satellite pictures. They can occasionally be astoundingly misleading. Once I had a perfectly clear night when the whole of SE France seemed solidly covered and once I had cloud and fine drizzle when it was showing perfectly clear. This is very much the exception but I've had these two examples over thast seven years. Don't risk your gear is my point...

I'm a little bit concerned that Sat 24 relocated Barcelona into France about a year ago and moved several North African cities into the Meterranean!!

Olly

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The best Satellite cloud images I've seen are the EUMETSAT Fog Images - http://oiswww.eumetsat.org/IPPS/html/MSG/RGB/FOG/WESTERNEUROPE/index.htm

It seems to be able to show the difference between clear skies and low cloud or fog.  Clear skies are pale magenta while fog is a sort of mustard yellow.  The usual IR images don't show the difference well because the temperature of the ground and fog is small.

Obviously not as reliable as looking outside.

Chris

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