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How to create a cloud sensor for a part of the sky?

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Just did a quick test with an old image. I saw many examples but used this one to see how it does on my usually too dark images. :-)
I think it is fairly easy to either analyse the guider images or the real images and do a prediction of cloud coverage once the star-count has dropped significantly.

To be continued.....
3 years 6 months ago #59545
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You can get the MLX90614 (cloud sensor part of the Weather Radio) in narrow field of view version. The standard part has a 90 degrees FOV but the MLX90614 is also available in 10 or even 5 degrees FOV.

What I am coming at is that a specialized/limited version of the Weather Radio could be built with a narrow FOV MLX90614 that would be put on the same axis and in from of the telescope tube. That could give you a good idea of the cloud cover in the FOV of the telescope, and the standard Weather Radio would give you an idea of the general cloud cover.

Ideally though, an all-sky (thermal?) camera with cloud detection/mapping over the KStars window would be preferred but... that's another story. :)
3 years 6 months ago #59546

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Hi Gerardvs
That's exactly what I thought of as an idea, so cool !!

The thing, now, it will be finished to integrate into kstars as we do for weather alerts.

But I think that on will have to add an additional camera, but that's not a problem, otherwise.

In all will I will wait impatiently to hear from you.

See you soon
Christophe
3 years 6 months ago #59547

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So I have the standard version of my weather station, by the way I didn't even know there was another angle.
3 years 6 months ago #59548

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I am not sure you can get the narrow FOV parts with evaluation boards like the Adafruit or DFRobot ones but they are available as discrete parts that you could use if you have soldering skills. Unless they are surface mounted on the evaluation boards, I am quite certain that one could replace the standard part with the narrow FOV one fairly easily.

If you are interested/curious, you can look at the Melexis datasheet for the MLX90614, www.melexis.com/en/documents/documentati...s/datasheet-mlx90614 .
3 years 6 months ago #59551

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I just found this interesting paper that could be relevant to what you want to do. It uses an all-sky camera (180 degree FOV) to estimate and map cloud cover for the observation of Cherenkov photons.

s3.cern.ch/inspire-prod-files-9/98f5d2c8...5cadd2963404c8ae5eec
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3 years 6 months ago #59552

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Hello
So indeed it looks good, but I admit not having understood all because my English is not as good as before.
Does he put a simple all sky style camera or is it an IR camera?

So the most, it is if you manage to make a correspondence between what the camera detects and manage to say that in 10min it will be covered in kstars.

But I think it's more complicated to set up than a star-counting camera, right?
3 years 6 months ago #59554

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I think the all-sky camera is not necessarily IR, a standard camera should be sufficient.

From what I get from the paper, a simple 1/0 detection/counting of stars (detected or not) will not take into account the possibility of light clouds through which some starlight could pass attenuated and be detected, leading to think that there are no clouds, thus giving a wrong estimation of the cloud cover. It may be interesting to evaluate the usefulness of coupling an all-sky camera star counting algorithm to a small FOV MLX90614 sensor to measure the "telescope pointed" sky temperature. You may still need to account for atmospheric effects and other factors but that's making for a more interesting/challenging project.
3 years 6 months ago #59631

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But don't you think that with an all sky camera you might have a problem with the rotation of the stars?
Whereas with a camera that always looks at the same place we should be more precise on the detection of clouds?
3 years 6 months ago #59633

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If by "a camera that always looks at the same place" you mean a camera that point in the same direction as the telescope, yes that would be easier and likely more precise but you will likely require a camera FOV that would make detecting incoming clouds possible, before they get in the FOV of the capture camera It should also be independant from the capture camera so it could monitor cloud movements while a capture is going on. That could be an interesting application for a PoleMaster that would be mounted on the optical axis of the scope.

Anyway, that's all food for thought.
3 years 6 months ago #59634

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Just posted, and saw this thread below mine, seems like a very similar thought to my mine - I wasn't consciously aware of this thread when I wrote mine, perhaps I'd unconsciously seen it over the last couple of days!
3 years 6 months ago #59636

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I just saw your post, interesting timing!

I had thought about the PoleMaster as, once polar alignment is done, the camera doesn't have a much useful purpose. Using any camera that has been replaced by a newer one is also a good idea for cloud (or visual obstacle) detection, as long as it's parallel to the optical axis of the scope and it has an appropriate FOV for the purpose. The simplest way do evaluate a change of condition would be to process subsequent images and check for differences at the edges of the frame, I assume. More involved processing techniques could probably get a better estimation of the sky conditions.

More food for thoughts! :)
3 years 6 months ago #59638

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