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A DIY Weather Observing Conditions device

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9 replies to this topic

#1 Mert

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Posted 03 April 2024 - 09:27 AM

Hi all,

 

Since I am always setting up my equipment either on my balcony or
when I go out to some dark site, I don't have a fixed setup.
When imaging the whole night, I wanted to have the ability to
switch off the equipment when ending the imaging session to

save battery.
For this I use a USB-switch board, and an Ascom driver I found
on internet that works with it.
So that gives me the option under advanced sequencer of NINA
to switch on/off some power outputs on my powerbox ( LifePo4
12V 100Ah  ).
When finished to wire that in and setup the sequences I would
like to be able to switch on/off some dewheaters when necesary.
So that led me to think about how to obtain the necesary
values for that into NINA.
The idea for a Weather Observing Conditions box plus driver
was born.
After quite some time working on the software side to write
an Ascom driver for it, right now I have the pleasure to be
able to automate my equipment almost completely and also

to have the option to obtain a logfile with all the measured

values from the whole session.
I have learned many things along this project and have had help
from very helpful people on the Ascom Developer group!
I am in the process of making a writeup for those who would
like to build something similar and will upload the Arduino
code and the Ascom driver to Github in case there is interest.

Not all of the functions of a Weather Observing Conditions
driver have been implemented because I use a mobile setup.
Therefore I left Wind, Rain, Cloudcover, Skybrightness and
Skytemperature out of it. ( I don't have a ROR observatory ).
Right now, it measures Temperature, Humidity, Dewpoint,
Atmosferic pressure, SQM and FWHM.

For the SQM value I still have to receive an UVIR filter to put

in front of the sensor but that will be very little effort.

Also still some problem when lower light levels then SQM19

are measured, busy with that.
The FWHM is under analisis and I will try to refine parameters
but for the moment it works nice using my Polemaster.
Here is a screenshot of what it measures for the moment.

 

Clear skies,
Mert

Attached Thumbnails

  • NANO-ObsCon box.jpg
  • NINA.jpg

Edited by Mert, 03 April 2024 - 10:28 AM.

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#2 PeteM

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Posted 03 April 2024 - 08:50 PM

Mert, this looks fantastic. Looking forward to seeing the writeup on it.



#3 Mert

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Posted 04 April 2024 - 10:41 AM

Thanks Pete, will certainly do that but first things first.
Right now it measures SQM values down to aprox 24 so that's more then enough.
Still have to calibrate the values, likely against ASTAP calculated SQM values.
Right now still a little flaw in the logging function of the driver that I have to address.

 

At the moment I use this setup when I image ( schematic ):

You can see the sensors wiring to the arduino nano and the

way I connect to my equipment.

 

 

 

Attached Thumbnails

  • NANO ObsCon.jpg

Edited by Mert, 04 April 2024 - 11:19 AM.


#4 Mert

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Posted 07 April 2024 - 05:05 AM

Here is my first "real" trial run, box mounted on a photo tripod looking at

the totally clouded sky through a window.

When the curve dips down to SQM 10 or alike is when I switched on the

lights.

 

Regards,

Mert

 

 

Attached Thumbnails

  • Trial run 060424 clouded.jpg

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#5 Arjan

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Posted 07 April 2024 - 09:26 AM

What's the SQM reading when you put the device in pitch darkness, like a box or so?

I have used a calibration factor to get it down to min detectable level at absolute dark. My sensor is not Taos, but AMS (now Osram), and has very high dynamic range: TSL2591.

I see AMS used to be Taos, hard to keep track of companies these days...

Edited by Arjan, 07 April 2024 - 09:51 AM.

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#6 Mert

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Posted 07 April 2024 - 02:57 PM

What's the SQM reading when you put the device in pitch darkness, like a box or so?

I have used a calibration factor to get it down to min detectable level at absolute dark. My sensor is not Taos, but AMS (now Osram), and has very high dynamic range: TSL2591.

I see AMS used to be Taos, hard to keep track of companies these days...

Hi Arjan,

 

When I put the meter in a box in a dark room with tape over the lens, it

gives me a value of 22.37

It is still without calibration so at the moment it is just a relative value  :shrug:

The sensor I use is a TSL237

I'm not sure which sensor would be more sensitive.

 

Regards,

Mert


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#7 Mert

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Posted 08 April 2024 - 02:02 AM

For completeness here is a log of a complete night.

I still have to go out to some dark site and do calibration to

get more exact values.

This log is also with clouds in the sky looking through a window

towards the city. ( quite bright greyish sky, almost like my

flatpanel at low brightness ).

 

CS,

Mert

 

 

Attached Thumbnails

  • Trial run 070424 clouded.jpg


#8 Mert

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Posted 10 April 2024 - 02:52 AM

Finally I had some relative clear night, now and then clouds rolling through.

So I setup themeter again and logged for the whole night from dusk to dawn.

Here you see the way I put the meter looking at the sky through a double glass

window.

Not optimal to do so but anyway, it is still not calibrated so precision right now

is not so important for me.

I configured to take a sample every 60 seconds.

 

Regards,

Mert

 

 

Attached Thumbnails

  • Test-setup.jpg
  • Trial run 100424 mostly clear.jpg

Edited by Mert, 10 April 2024 - 07:21 AM.

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#9 Mert

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Posted 20 April 2024 - 07:21 AM

Last night I left the equipment setup on the balcony and tried to do

some imaging meanwhile logging data.

On the minipc that controls the scope I had some weird USB item

that made me reboot it to get started again.

Moon was 83% lit so quit a bright sky.

I still have to calibrate the FWHM values a bit better. ( will

use Meteoblue predictions etc. )

There were a few clouds passing by during the night.

 

 

Attached Thumbnails

  • ObservingConditions.jpg

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#10 Mert

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Posted 21 April 2024 - 11:37 AM

Yesterday I did some calibration on the FWHM measurements and got a

reasonable result compared with Meteoblue.

Of course the seeing from my balcony is not the same as when I

setup in the field ( in the same village ).

 

Here is a graph from the logfile over some 163 samples.

Values are in arcseconds.

 

 

 

Attached Thumbnails

  • Seeing FWHM 200424.jpg



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