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johnpd
sage


Reged: 04/13/08

Re: iPhone 'SQM' app available soon ... your thots? new [Re: derangedhermit]
      #5721552 - 03/09/13 03:05 AM

Quote:

With the wide field of view, how do you account for the brightness of the Milky Way (or lack of same) in the field?




I know the Milky Way affects the values on my SQM. Readings give a brighter result.

JohnD


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core
Pooh-Bah
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Reged: 02/23/08

Loc: Mostly in Norman, OK
Re: iPhone 'SQM' app available soon ... your thots? new [Re: Madratter]
      #5721633 - 03/09/13 04:39 AM

Quote:

I don't even care all that much if it is calibrated for it. I just want an objective measure




fwiw, to get a objective measurement will require a calibrated reading; an un-calibrated reading gets you subjective reading - if using the same device, then you can get a subjective night-to-night difference in reading, but you can't give it an objective visual magnitudes per square arcsecond.


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dan777
scholastic sledgehammer
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Reged: 11/16/07

Loc: Indiana
Re: iPhone 'SQM' app available soon ... your thots? new [Re: core]
      #5721924 - 03/09/13 10:06 AM

Quote:

an un-calibrated reading gets you subjective reading - if using the same device, then you can get a subjective night-to-night difference in reading



Not really. If you have an instrument with good repeatability but a DC offset, you will get objective data. As long as you don't care about absolute accuracy, you can use it to compare tonight's sky with last night's sky and get objective data. Using your naked eye to compare tonight's sky with last night's sky will give you subjective data.

BTW, thanks for the heads-up on this app.


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core
Pooh-Bah
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Reged: 02/23/08

Loc: Mostly in Norman, OK
Re: iPhone 'SQM' app available soon ... your thots? new [Re: dan777]
      #5722165 - 03/09/13 12:00 PM

Might be a matter of semantics on my end , but say if a measuring tape is off by +0.5", I couldn't measure my mirror and say objectively that my mirror is 8.5" diameter (and likewise "my SQM reading at my backyard was 19.9 last night"). There might be the issue of linearity as well, perhaps something on the hardware end (gain/AGC) that imposes a non-linear transfer function.

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Madratter
Postmaster


Reged: 01/14/13

Re: iPhone 'SQM' app available soon ... your thots? new [Re: core]
      #5724649 - 03/10/13 08:04 PM

I think there is some confusion going on here between accuracy, precision, and objectivity.

Objective would normally mean that the reading does not depending on the person using the tool.

http://wiki.answers.com/Q/What_is_the_meaning_of_the_scientific_word_objective

"Scientific objectivity means that independent observers, using the same procedures, will come to consensus regarding the phenomenon they are studying. In other words, personal opinions, values, and biases will not change observations recorded with scientific objectivity."

Precision is how many digits are reported in a measurement.

Accuracy is how much error there is in a measurement.

In this case, I want the app as long as it is objective and repeatable, even if it isn't particularly accurate.


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derangedhermit
Pooh-Bah


Reged: 10/07/09

Loc: USA
Re: iPhone 'SQM' app available soon ... your thots? new [Re: johnpd]
      #5725178 - 03/11/13 03:27 AM

Quote:

Quote:

With the wide field of view, how do you account for the brightness of the Milky Way (or lack of same) in the field?




I know the Milky Way affects the values on my SQM. Readings give a brighter result.

JohnD



Yes, the SQM-L lets you point outside the Milky Way for readings, since it has a narrow field of view. Maybe the app lets you pick a portion of the image for the measurement, or to exclude. Otherwise I think it would be of little value.


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dan777
scholastic sledgehammer
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Reged: 11/16/07

Loc: Indiana
Re: iPhone 'SQM' app available soon ... your thots? new [Re: derangedhermit]
      #5725391 - 03/11/13 08:55 AM

Quote:

Otherwise I think it would be of little value.



What if you can't see the milky way?


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Nop
Vendor (iPushto)


Reged: 02/12/06

Loc: Netherlands, Valkenburg
Re: iPhone 'SQM' app available soon ... your thots? new [Re: dan777]
      #5727410 - 03/12/13 03:49 AM

FYI: We don't use the full frame in the app. The FOV is about 20degrees. We are still testing and adjusting.
We could substract the milky way influence by a formula. If the skies apppear to be dark, and the brightest parts of the milky way are in the Zenit, and the device is pointed at the Zenit. a correction value can be applied. But that can be tricky..


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core
Pooh-Bah
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Reged: 02/23/08

Loc: Mostly in Norman, OK
Re: iPhone 'SQM' app available soon ... your thots? new [Re: Madratter]
      #5727792 - 03/12/13 10:17 AM

Quote:

I think there is some confusion going on here between accuracy, precision, and objectivity.




Succinct and to the point, thanks for clearing it up!

Dan, I'd suppose if you can't see the Milky Way (assuming it's there and skies are clear) - that would probably mean the local LP levels are above the glow of the MW - in that case the SQM reading will be reading that glow signal which is above that of the MW's.

Norbert, thanks for the update on the app's FOV spec - a concern might be a confusion when users are reporting back SQM readings (especially to IDA) - the current SQM and SQM-L have fixed FOV and calibrated/temp compensated readings. Also, having the app take into account any Milky Way glow reading would skew the results, considering 1) the SQM meter does not do that 2) MW glow is not consistent across FOV.


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johnpd
sage


Reged: 04/13/08

Re: iPhone 'SQM' app available soon ... your thots? new [Re: Nop]
      #5728762 - 03/12/13 06:36 PM

Last night's numbers were above my SQM readings for the first time. Usually the app's numbers were lower. If we can find the happy medium, we are in business.

JohnD


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dan777
scholastic sledgehammer
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Reged: 11/16/07

Loc: Indiana
Re: iPhone 'SQM' app available soon ... your thots? new [Re: johnpd]
      #5728846 - 03/12/13 07:21 PM

Quote:

Last night's numbers were above my SQM readings for the first time. Usually the app's numbers were lower. If we can find the happy medium, we are in business.



But was each device measuring the same FOV (not just total area, but same length and same width)?


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Nop
Vendor (iPushto)


Reged: 02/12/06

Loc: Netherlands, Valkenburg
Re: iPhone 'SQM' app available soon ... your thots? new [Re: dan777]
      #5729727 - 03/13/13 06:04 AM Attachment (20 downloads)

@JohnD
I've updated the 5's algorithm.
FYI
We have provided a little 'tweaking' setting in the iPhones settings menu (look for dark sky meter). That can compensate structural differences between camera's. It's a kind of calibration. Say, the structural difference between your sqm and the dark sky meter is 0.1, just set the value (positive or negative) in the settings field.

Edited by Nop (03/13/13 06:26 AM)


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johnpd
sage


Reged: 04/13/08

Re: iPhone 'SQM' app available soon ... your thots? new [Re: Nop]
      #5730899 - 03/13/13 06:50 PM

Nice job Norbert. I will test the latest version (#38) tonight and see if I can come up with a good offset if needed.

JohnD


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Nop
Vendor (iPushto)


Reged: 02/12/06

Loc: Netherlands, Valkenburg
Re: iPhone 'SQM' app available soon ... your thots? new [Re: johnpd]
      #5761793 - 03/28/13 06:47 AM Attachment (19 downloads)

A little heads up. This is a screenshot of the free Public Outreach 'lite' version aimed at a broad audience with the goal to provide tons of measurements worldwide.. It uses an approximate scale, no output in SQM/NELM and lacks the maps and weather features of the pro version. But this version will submit detailed measurements to researchers and the folks at the IDA.

Edited by Nop (03/28/13 06:47 AM)


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johnpd
sage


Reged: 04/13/08

Re: iPhone 'SQM' app available soon ... your thots? new [Re: Nop]
      #5763612 - 03/29/13 04:00 AM

Hi Norbert,

You say that the Lite version does not give a SQM value? I know the last one I tried just gave a poor/good/etc value. I am thinking of its value for submitting readings to the Globe at Night site. School kids could use the Lite version for that if a SQM value was available or there was some way of sending that value to the site.

JohnD


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Nop
Vendor (iPushto)


Reged: 02/12/06

Loc: Netherlands, Valkenburg
Re: iPhone 'SQM' app available soon ... your thots? new [Re: johnpd]
      #5763614 - 03/29/13 04:05 AM

Hi John,
The SQM / NELM user feedback is in the Pro version. But in the lite version it's under the hood. The lite version submits these values as hi precision SQM values, along with position, pointing etc. The only difference is that these values dont show up in the user interface. These values can and will be used by the IDA and other parties. For instance Globe at Night. The added value is in the data. Therefore the app should be as simple as possible, attractive, free for the masses. Like we did with the VenusTransit app. More than 130.000 downloads in 2 weeks generating lots of useful data and raising awareness worldwide.

A sample of the data submitted:

datetime latitude longitude moonperc device deviceangle devicesqm
28-03-13 50,8 5,8 99 iPhone5,2 89 20,82

You can see that even the moon percentage is calculated, and if the device is correctly pointed towards the Zenit.

Edited by Nop (03/29/13 04:14 AM)


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Jon Isaacs
Postmaster
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: iPhone 'SQM' app available soon ... your thots? new [Re: Madratter]
      #5763749 - 03/29/13 07:25 AM

Quote:


"Scientific objectivity means that independent observers, using the same procedures, will come to consensus regarding the phenomenon they are studying. In other words, personal opinions, values, and biases will not change observations recorded with scientific objectivity."




How about the biases in the procedures themselves? Any errors in the procedures, systematic or otherwise will be propagated. That would seem to be the problem here. It would seem that understanding a phenomena requires the use of multiple procedures/techniques that then converge on an understanding/consensus.

Myself, I would want an app that is reasonably accurate...

Jon


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johnpd
sage


Reged: 04/13/08

Re: iPhone 'SQM' app available soon ... your thots? new [Re: Nop]
      #5765710 - 03/29/13 08:44 PM

Hi Norbert,

Where would this data be submitted to so that a person could get at it and then use it to fill out the Globe at Night Reporting page?

JohnD


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crazyqban
Carpal Tunnel
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Reged: 12/16/08

Loc: Miami, Florida
Re: iPhone 'SQM' app available soon ... your thots? [Re: johnpd]
      #5765920 - 03/29/13 11:19 PM

Hello Norbert, any news on the release date?

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core
Pooh-Bah
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Reged: 02/23/08

Loc: Mostly in Norman, OK
Re: iPhone 'SQM' app available soon ... your thots? new [Re: crazyqban]
      #5768003 - 03/31/13 01:31 AM

I suppose it's a kind of catch-22. For the 'free' version, the user doesn't get any SQM or NELM numbers displayed; however this SQM reading is transmitted to IDA (with user's permission). The user only gets a descriptive "The sky is X time brighter ..." You can't check or calibrate the SQM app to an actual SQM device with the free version - for that you will need the paid version, which will then allow you to see the actual numerical SQM acquired. If there is enough device-to-device variation, I can foresee some issues with regards to the quality of data submitted to IDA via the 'free' version, especially since one would expect that there would be a lot more of those running compared to the paid version. In that case, perhaps another piece of data that should be submitted by the app to IDA is the calibration offset, and paid/unpaid status.

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