Sky Quality Meter

[Star Dad]

I am a ranger for The Last Green Valley (in CT - a National Heritage Corridor) and TLGV is looking to purchase Sky Quality Meters to measure and track our dark skies - and/or loss thereof. I have been given a SQM from Unihedron (Grimsby, Ontario). Does anyone know of the quality of this meter and/or suggestions for meters? We are planning on buying a few of them for various other rangers to use (read this as needing to be friendly for technically challenged people).

[Lady Fraktor]

I believe they are the most common maker of these, they are normally the make you see people using in the field.

[Star Dad]

Thank you. I tried using it last night in my "dark area" at home. My hometown is rated at 19.95 - I got 20.12-20.14; so it was pretty close. Guess I have to get a database set up to record the data.

[Lady Fraktor]

The 19.95 may be an average over a year.

[JayTee]

I own the Unihedron SQM-L. I use it all the time and trust the readings it provides. I like the fact that the -L version looks at a smaller chunk of sky. I usually take several readings in each quadrant of the sky so I can average them out to get a more accurate assessment of the current level of darkness.

Cheers,
JT

PS, I am currently vacationing in Teton Village, WY and went to a close-by dark site with my meter and got an average reading of 21.63 and I had a NELM of 6.2. Boy, is it dark out here! jt

[Star Dad]

Thanks for the advice.

[yobbo89]

I thought about getting one but after seeing peoples results compared to online data which is pretty close to.other then determining exposure settings for imaging is there any reason to get one? , i've seen post online where people have shopped for housing location with a sqm !

[Lowjiber]

Living in the supernova that is Las Vegas, I've found the SQM-L to be a nice-to-have tool in my box. The Vegas light-dome is visible even 125 miles away in the dark desert. I've recorded, directional, readings of over twenty various desert viewing sites that provide quantitative comparisons.

Clear, Dark Skies

[DeanD]

Thank you. I tried using it last night in my "dark area" at home. My hometown is rated at 19.95 - I got 20.12-20.14; so it was pretty close. Guess I have to get a database set up to record the data.

We have been using the Unihedron wide-angle version for a number of years to confirm dark sky sites etc. They are a great way of providing objective data, and very helpful in seeking community and government support to maintain sky quality.

Your hometown rating of 19.95 must, as Gabby says, be an averaged reading because the readings will vary during the night and from season to season, so an ongoing database is an excellent idea. They will also vary according to the part of the sky they are pointed at, so it is good to average them for recording purposes. As an example, at the last dark-sky camp I attended in the Flinders Ranges in South Australia, the readings were as "low" as 21.6 when pointed at the centre of the Milky Way (which was directly overhead at the time), and as high as 22.1 in other quadrants of the sky; but the darkest readings varied from 21.8-22.1 during the night. (Interestingly we could tell when it got "darker" even without the SQM: our vague shadows cast by the Milky Way became easier to see... That's a dark sky JT! )

During the time of solar max, a number of years ago, the readings rarely went higher than 21.7. I think possibly due to upper atmosphere glow caused by higher solar emissions.

All the best,

Dean