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SQM meter for iPhone

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#1 Becomart

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Posted 19 August 2019 - 07:06 PM

Just thought it was worth a post to give a shout out to a new app I’ve discovered for measuring sky quality. It’s called ‘dark sky meter’. It had a few good reviews and is apparently fairly accurate when compared with an sqm meter which can cost a fair bit. Just been out to test it and it consistently gave a reading of 20.63 which I’m quite happy with considering the moon is blasting through the sky. Will try it again on a darker night as I’m in bortle 5 skies (not far off 4). 


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#2 Taosmath

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Posted 19 August 2019 - 07:31 PM

Just looked - there doesn't seem to be an android version frown.gif



#3 wcoastsands

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Posted 19 August 2019 - 08:00 PM

Very cool. Looks like it requires a network connection to function properly, though. Relies on a web backend.

https://apps.apple.c...ter/id602989060

#4 Ron359

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Posted 19 August 2019 - 08:17 PM

Just looked - there doesn't seem to be an android version frown.gif

There are far too many versions of android cameras for the developer to be able to make it work for.  

 

BTW -there are several threads in the LP forum about the DSM app, including posts by the developer.    I think it only needs a cell network if you want to send in the readings to the international data base as you take them.  


Edited by Ron359, 19 August 2019 - 08:20 PM.

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#5 PeteM

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Posted 19 August 2019 - 08:41 PM

Nice that it is back. I got the app years ago and then the developer stopped developing it and pulled it from the app store. So I just open up the wallet and got a SQM-L. Honestly, really wished I got the SQM-L years ago.


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#6 17.5Dob

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Posted 19 August 2019 - 10:15 PM

No cell signal at any of my dark sites....and I don't own a "Smart Phone"....



#7 AhBok

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Posted 19 August 2019 - 11:02 PM

I use it and have compared it with my old SQM several times. The readings are close enough and definitely repeatable. The small difference between it and the SQM is fairly linear over a range of sky brightness. Pretty neat.
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#8 2ghouls

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Posted 20 August 2019 - 07:14 AM

The readings are close enough and definitely repeatable. The small difference between it and the SQM is fairly linear over a range of sky brightness.


I found it to be more optimistic than my SQM-LU, but yes there was a consistent offset. So on nights I’m not using my Unihedron, I can just use the app and apply the offset in my head. Very useful and worth the $2.

I am pretty sure it has a much wider FOV than the Unihedron devices so probably best to use it at zenith only and not for measuring light domes on the horizons.
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#9 Alex McConahay

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Posted 20 August 2019 - 08:25 AM

So just how large are these offsets you speak of?

 

Alex



#10 AhBok

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Posted 20 August 2019 - 09:31 AM

For me, .2-.4 across a range of altitudes (sky brightness). I think 2 ghouls is right on about the FOV differences. The delta is least when pointing directly at the zenith.

#11 fishonkevin

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Posted 20 August 2019 - 09:41 AM

There is an Android version called " Black Sky Meter".  I have not downloaded it yet, but the description does look promising.



#12 Alex McConahay

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Posted 20 August 2019 - 09:53 AM

Is the.2 o .4 random, or always brighter or dimmer than the dedicated meter?

 

Undoubtedly the wider field of view could easily dilute the peak darkness at the meridian with brighter lower altitude light, making it read brighter overall. 

 

Alex



#13 nimitz69

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Posted 20 August 2019 - 10:41 AM

well I Always have my SQM when doing any kind of Astronomy but it would be neat to have access to SQM readings pretty much any time anywhere and not have to carry my SQM around to do that ... another $2 I'll never see again dalek12.gif


Edited by nimitz69, 20 August 2019 - 10:42 AM.


#14 2ghouls

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Posted 20 August 2019 - 10:46 AM

Is the.2 o .4 random, or always brighter or dimmer than the dedicated meter?

 

Undoubtedly the wider field of view could easily dilute the peak darkness at the meridian with brighter lower altitude light, making it read brighter overall. 

At my old club in Delaware, we installed it on three iPhones, and they were all pretty consistent (within about +-0.2) pointed straight up at the zenith. The closer you pointed to the horizon, the more inconsistent the readings were across iPhones, but also just measurement to measurement.

 

At zenith, My Unihedron SQM-LU had consistently brighter readings of approx. 0.4. So, the offset to correct the app was -0.4.

 

I do find it convenient for quick measurements, and if you have an iPhone, I think it is a great buy. It won't replace a dedicated meter if you are interested in more intensive LP studies. If you are in the market for a meter, I would wait until later this Fall, Sergey from Astromechanics will be releasing the next version of his meter with a much narrower FOV. I am looking forward to it.


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#15 AhBok

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Posted 20 August 2019 - 12:18 PM

Your experience and opinion mirrors mine. I like it just for having a quick relative reference of sky brightness for a given time on a given evening.


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