Telescope Reviews: Received my new Sky Quality Meter; NOW WHAT?!

Because darkness and acuity of vision are not related, the answer would be no.

My recent acquisition of distance glasses that correct my vision to 20/05 allows me to see considerably fainter stars with the naked eye than I ever have seen in my entire life, even though I had 20/20 distance vision before.
I would usually be able to see the mag.6.2 star near Polaris (translating to 6.4 zenith) with averted vision, on the same night I'd see past magnitude 15.5 with my 8" scope. Moving backwards from the limiting scope magnitude to naked eye, I should have been able to see 7.5 with the naked eye. But I never could.

Now, I might be able to. I recently counted 12 stars in the Pleaides, naked eye.
So, I'm going to explore the AAVSO charts to see how faint I can see.
But, since visual acuity so radically determines how faint a star you can see (ostensibly by concentrating its light into a small point instead of a smear), darkness measurement will only allow fainter stars to be seen if one's vision is exemplary.

I once did a count of the stars in the Great Square of Pegasus to determine how faint I could see (from an old S&T article), and got to 6.5 on a night where a friend of mine couldn't reach mag.6.0. The sky was the same for us, yet the stars we could see were different. My vision proved better. A younger person with better vision would probably have seen even fainter stars.

But there are valid reasons for you to get a brightness measuring device:
--to measure changes over the years and compile data for your site
--to measure changes with solar cycle
--to correlate darkness with what you can see (NE or scope)
--to have a record of correspondence between darkness and observations (in your notes)
--to create a personal comparison between NELM and darkness
--to see if darkness and clarity (absence of aersosols in the air) correspond at your site.[they don't, at mine]
--to compare your readings with the light pollution maps
--to submit data to the light pollution map people to better simulate an accurate map in your area
--to provide you with non-subjective data
--to allow you to "tune" your observing session to better use your time (e.g.if the sky is a half magnitude brighter than normal, why seek the faintest galaxies your scope can see?)

To name a few (I also have a test report on Cloudy Nights you might read to get some ideas).

Now, of course, you can easily use math to convert brightness per square arc-second to brightness per square arc-minute (the more familiar figures), but how the brightness per square arc-minute compares to the naked-eye view is equally obtuse.

The brightness per square arc-second figures shown on the light pollution maps on the Clear Dark-Sky Clocks do not correspond to what I see because I observe at high altitude. They mention that the data is inaccurate for high altitude, but I think you cannot correspond the Bortle Scale to sky brightness without taking extinction into account. Two sites with the same sky brightness could have very different extinction coefficients, and this would result in the subjective Bortle Scale determinations being different for the two sites. Ergo, you cannot match brightness to the Bortle Scale, as they try to do in the maps, unless you can also add the figure for extinction.

It is possible to modify the SQM to measure extinction. I'm working on that modification now, and will post my results after more testing.

Don

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Don Pensack
12.5" Truss Dob, 5" Maksutov
Sustaining Lifetime IDA member, TeleVue junkie