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SilverAstro

Clear Sky, IR or Thermal

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I need a device to :

1) show me the sky when I am sat by the fireside. To save me getting up every few minutes to look out the door ! So I am watching the AllSkyCamera peeps and how they are getting on.

2) detect a reasonable patch of clear sky and wake me up when in bed, or asleep by the fireside !

Would an IR modified Canon (from the likes of Cheapastro ) do both jobs or would I need a thermal imaging device to do (2)

I guess what I am asking is - does the IR sensitivity of a Canon sensor go far enough into the thermal end of IR to detect the cold-of-clear-sky / warmth-of-clouds ? If not does any one know a suitable device and how many arm&legs it would be ?

Somebody living under British Wx must have done this already ? :)

 

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48 minutes ago, cjdawson said:

Rather than using an all sky camera.

How about building a cloud detector, here's a link to one that I found. (don't know if it works, just wanted to show an example)

http://www.noao.edu/staff/gillespie/projects/cloud-detector.html

 

I think it would be much less prone to getting taken by dirty rotten theives-es

Very interesting thanks for that, not come across the idea of a backwards peltier before.

I have seen ( and was going to try, without much hope cos of surrounding trees and bushes and not an enormous size of sky :( ) differential ground/air temperature devices based on transistor and/or diode, but not many peeps extolling their use/virtue and the same with the spot IR metering devices. So on the basis of if it was as good as sliced bread we'ed all be eating them lol! :)

As for dirtyrotten, non round here ! we leave the keys in the cars, can go out without locking up have done for 40odd y - - but now that I've told you all, tomorrow may be a new day ! Where's some wood to touch ;) mind-u it would be an enterprising lowlife that could find a camera in my garden !! amongst all the hazards and man-traps, even I loose stuff :) but good point, thanks for the warning :)

 

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Someone at the Farnham Astronomical Society has made a DIY one so they might be worth getting in touch with, all depends just how technically minded you are when it comes to Raspberry Pi and doing your own coding. I'm currently making my own software to operate all sky cameras which is far less difficult than i imagined it might be, google is a wonderful resource.

http://www.farnham-as.co.uk/2013/04/building-a-cloud-sensor/

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5 minutes ago, purgitoria said:

Thanks, I will read that with interest

"non-contact thermometers" ah ! thems the words I wanted not "spot IR metering", I looked at them some years ago and the were much too expensive back then, better now ! But I think there was a problem with moisture/rain getting in and putting a cover on it defeated the purpose by it measuring the temp. of the cover, lets see how this fella manages > > >

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I have a cloud sensor project on the books but it's shelved ATM.  Far far toooooo many projects...  And I just keep adding to the list!!  I just muddle on and on :D

Edited by Gina

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1 hour ago, Gina said:

 shelved ATM.  Far far toooooo many projects...

I dont know, dear oh dear, excuses excuses, youngsters these days, tsk tsk ! :laughing4::angel8: Yep, I know the feeling, and as winter approaches the fireside looks ever more attractive :)

Does your allsky cam always show clouds as white at night regardless of moon/no moon, you are in a pretty dark place like me, what about low down heavy dark-in-daytime type clouds, do they show white  I am wondering if it needs some light pollution to distinguish them from empty black sky. Cos if the RasPi camera is not sensitive enough to show stars in the clear patches it may still be good for showing dim clouds ? However even if not the RPi, there should be plenty of ellcheapo Canons out there by now !

Edited by SilverAstro
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There's no such thing as empty black sky here!!  Wherever there is no cloud there are hundreds of stars.  Generally cloud will show lighter.  In daytime with a mono camera it is difficult to tell if a dark area is black cloud or clear blue sky but there is no problem at night.  No stars means cloud or fog.  The brighter stars will show through light cloud.

IR cloud sensors work by detecting the IR reflected by clouds from the warm earth, I believe.

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21 hours ago, purgitoria said:

Someone at the Farnham Astronomical Society has made a DIY one http://www.farnham-as.co.uk/2013/04/building-a-cloud-sensor/

I'm currently making my own software to operate all sky cameras which is far less difficult

And then abandoned it ! :( (see very last comment on the page) due to moisture, that seems to be a common hazard with those IR projects / devices :)

Yes, I have done a fair bit of coding in my time :) +electronics and stuff, it is all that keeps an astronomer me sane during cloudy nights ! Would love to see/follow how you get on with your camera. Good luck.

 

Edited by SilverAstro

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The IR cloud sensor detects sky temperature and when it is clear it will read -30ish and when cloudy it will read the temperature of the clouds, I assume it will be reflecting a certain amount of heat that would normally rise and hence detects that or reads the temperature of the clouds (probably a mix of the two). It cloudy conditions the temp will read 12 deg.

You could use the MLX90614 sensor and they come with 45 deg views or 60 deg view - you need to check the wavelength of ir it detects i think it's 5-14 wavelength range.

The only problem I have is dew as I've never been good at getting rid of it. You need to put a rain sensor with heater element inbuilt next to the ir sensor to keep both clear.

If you get an MLX90614 a couple of resistors, capacitors and an arduino you can have one up and working in a couple of hours - including the usual time fluffing around because you have the wires wrong and the baud rate doesn't match.

 

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On 12/8/2016 at 16:48, Gina said:

I have a cloud sensor project on the books but it's shelved ATM.  Far far toooooo many projects...  And I just keep adding to the list!!  I just muddle on and on :D

To be honest it won't be very challenging for you Gina! It's relatively easy and you'd have it sorted in between breakfast and mid morning tea ;-D

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I may have a go at this later but ATM there are more pressing projects on my list involving stuff for actual imaging.  OTOH there's always the chance that I'll have a sudden brain storm and decide I want to do that little project :D  This happens now and then...

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On 12/08/2016 at 12:24, SilverAstro said:

Would an IR modified Canon (from the likes of Cheapastro ) do both jobs or would I need a thermal imaging device to do (2)

I guess what I am asking is - does the IR sensitivity of a Canon sensor go far enough into the thermal end of IR to detect the cold-of-clear-sky / warmth-of-clouds ?

 

Just so we dont get too tangled between my two topics ! (my thoughts often tangle ! :) )

This one (OP) was meant to be mainly about the ability of the Canon camera sensor to do thermal imaging (or not, as an off shoot of its ability to do skycam as well), or about other IR/thermal imaging devices.  (rather than spot IR or environment temperature devices.)

 

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