Data Logging SQM

[MarkS]

I've got a new toy - a data logging Sky Quality Meter.

Last night was too windy for imaging and the transparency was poor (Sahara sand and Iberian smoke) but I left the meter running all night with a dew band to prevent it misting up:



The blip in the curve at 20:30 was caused by a cloud.  Probably the same thing happened at 3:45am.

Mark

[JohnP]

Nice...

[Carole]

Where did you get it Mark, I could do with showing how carp it is in Bromley these days.

Carole

[MarkS]

It's this version:
https://www.firstlightoptics.com/unihedron-sky-quality-meters/unihedron-sqm-lu-dl-sky-quality-meter-with-usb-and-data-logging.html

But it is designed for continuous logging - it doesn't have a visible display like the standard model has.

Here's the standard hand-held one with a visible display but without data logging:
https://www.firstlightoptics.com/unihedron-sky-quality-meters/unihedron-sqm-l-sky-quality-meter.html

Mark

[Carole]

Thanks Mark, was not expecting them to cost quite that much.  I probably only want to use it for a one off use just to see how bad my skies really are.

Carole

[The Thing]

Do the two models agree on readings?

[MarkS]

Do the two models agree on readings?

The data logging one comes with a calibration certificate.  I pleased to see that my handheld one agreed with it to within 0.1 mags
Mark

[Carole]

Roger has lent me his SQM as I wanted to see just how bad the skies are in Bromley.
Looking at this chart, it is not good:
http://unihedron.com/projects/darksky/Instruction_sheet.pdf

@ approx 7.15pm = 17.16.

@ 10.30 = 18.36

Carole

[ApophisAstros]

Interesting piece on SQMs.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3821345/
Roger

[MarkS]

Roger has lent me his SQM as I wanted to see just how bad the skies are in Bromley.
Looking at this chart, it is not good:
http://unihedron.com/projects/darksky/Instruction_sheet.pdf

@ approx 7.15pm = 17.16.

@ 10.30 = 18.36

Carole

Your reading of 18.36 translates into a naked eye limiting magnitude (NELM) of around 4.3

This description of a city sky from http://www.skyandtelescope.com/astronomy-resources/light-pollution-and-astronomy-the-bortle-dark-sky-scale/ seems appropriate:
"The sky glows whitish gray or orangish, and you can read newspaper headlines without difficulty. M31 and M44 may be barely glimpsed by an experienced observer on good nights, and only the bright Messier objects are detectable with a modest-size telescope. Some of the stars making up the familiar constellation patterns are difficult to see or are absent entirely. The naked eye can pick out stars down to magnitude 4.5 at best, if you know just where to look."

Mark

[Carole]

When I first started imaging you could clearly see the major stars, and major constellations like the plough, Cassiopeia, Cygnus and Orion, could even see the Orion nebula naked eye as a fuzz, also M45.  These days I can hardly see any of Cass, Plough and M45 and only if I know where to look as they are very faint.  I can see the summer triangle, but have to look hard to see the other stars in Cygnus.  Orion is not as defined as it was. 

I always thought I was Bortle 8, so this confirms it. 

Very depressing, thus the need to get regularly to DSC. 

Carole