Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

Piero

How dark is your sky on a moonless night?

Recommended Posts

My sky is very good when the clouds clear off and even better after rain has cleaned things up a bit. I can see M33 naked eye but not every clear night. I have also seen M41, M13, M 6 and M7 as patches of light some nights though not often as apart from M13 they are fairly low down and things need to be top draw for that.

Share this post


Link to post
Share on other sites

I've been using this to check my sky's from my terrible back garden...

20160501_082614.jpg

After 5 min dark adapting in my shady spot I could make out 10 stars giving me around 5 or 7 on the bortle scale..

What I will say is I can and have easily made out the double cluster and m31 easily on the better nights, the later with averted vision but enough to point the finder scope straight at it.

So I hope with a bit more time adapting I might manage a bit better... 

Must go and check my dark site some time..

Ta

Fozzie 

  • Like 3

Share this post


Link to post
Share on other sites

Doesn't sound too terrible Fozzie! ?

  • Like 1

Share this post


Link to post
Share on other sites

Considering I'm not too far from street lights, I'm happy.. love observing with the fraction more than the newt as it cuts through better... I'm on the edge of town with practically nothing north so 20 mins drive and it's a different confusing world of stars and glowing milky way! Will check again when I get more dark adapted and report back!

Ta

Fozzie

Share this post


Link to post
Share on other sites
4 hours ago, Stu said:

I reckon that must be wrong Derek. I'm sure your skies would at least be as good as mine, probably better. What's your NELM?

I got a reading of 18.3 later in the session, Stu.

How do I measure NELM?

Share this post


Link to post
Share on other sites
10 minutes ago, DRT said:

I got a reading of 18.3 later in the session, Stu.

How do I measure NELM?

Easiest way is with Fozzie's chart above

Share this post


Link to post
Share on other sites

This is the rest of the scale if anyone's needs/interested..

20160501_114141.jpg

Ta

Fozzie 

 

  • Like 2

Share this post


Link to post
Share on other sites

Measured at Kielder earlier this year the reading was something like 22.35 measured on a proper meter by Rob Ince. He will confirm this or correct me if asked I am sure. I have just downloaded the app for the IPhone so will try it if I remember tonight here in the North East.

Derek

Share this post


Link to post
Share on other sites

thanks for the chart Fozzie ill post here too when get a chance

Share this post


Link to post
Share on other sites

Reading of 18.69 and NELM of 5.40m South Shields. Done on IPhone 4 using  at 23.36 hrs.

partially cloudy.

Also tried aiming off towards Newcastle...... Got a figure of 15.69 !

Just a load of sky glow really so means nothing as not directly overhead.

Share this post


Link to post
Share on other sites

How good are these meters? Take lightmeters for example, I used to have one that cost about 300 quid but it did flashmetering as well, I would like to think it was more acurate than a cheap one.

BTW my NELM last night was about 1.0, I could just see Spica:icon_biggrin:.

Alan

Share this post


Link to post
Share on other sites

Well the software for the IPhone says that it can give the wrong readings. I suppose it depends upon how  carefully you get the dark reading before the actual measurement, then how good the IPhone is. Still it is an indication. Last night there was very slight cloud cover with  small clear patches in between. I aimed for the clear patches overhead. Actual readings varied from 15.4 ish earlier on up to the final few that I took later on. I could see no stars at all though. So must have been some higher wispy cloud cover. On the best clear nights all I can see is the outline of the Plough and the main stars in Orion. None of the dimmer stars are ever visible. If I had a proper meter I guess  the readings would be different from those of the IPhone app.

Roll on our move to darker skies.

Derek

  • Like 1

Share this post


Link to post
Share on other sites

I downloaded the app Dark Sky Meter and it seemed to be reading SQM 18.75 consistently.  App says this is 5.44 NELM.  I just did an exercise out of curiousity to look at the handle area of the Big Dipper near zenith with a little "cool down" time for the eyes.  In Ursa Major, I can see 83 [4.7] and 82 [5.5] just barely with averted vision.  So it's pretty much average/decent suburban skies.  

Are we looking at the right thing with the unihedron table?  If I use the converter for 5.5 NELM it returns 20.0 MPSAS which can't be the same as SQM.  I'd be publishing much more exciting reports from here if I was at 20 SQM!

Edited by Special K

Share this post


Link to post
Share on other sites

Wooo, tonight I saw 22.10 on the SQM, the first time ever over 22. Alas it was a one-off reading, the consistent value being in the 21.76 region. Still it was nice while it lasted!!

Olly

  • Like 2

Share this post


Link to post
Share on other sites
On 1 May 2016 at 12:38, Physopto said:

Measured at Kielder earlier this year the reading was something like 22.35 measured on a proper meter by Rob Ince. He will confirm this or correct me if asked I am sure. I have just downloaded the app for the IPhone so will try it if I remember tonight here in the North East.

Derek

Can't find the iPhone App.  "Dark Sky Meter" on the App Store. Can anyone tell me what the app's title is?

thanks

Share this post


Link to post
Share on other sites
8 hours ago, ollypenrice said:

Wooo, tonight I saw 22.10 on the SQM, the first time ever over 22. Alas it was a one-off reading, the consistent value being in the 21.76 region. Still it was nice while it lasted!!

Olly

Take your finger off the end of the meter next time Olly ??

  • Like 2

Share this post


Link to post
Share on other sites
5 minutes ago, Ceramus said:

Can't find the iPhone App.  "Dark Sky Meter" on the App Store. Can anyone tell me what the app's title is?

thanks

It's exactly that, you should find it

image.jpeg

Share this post


Link to post
Share on other sites
1 hour ago, Stu said:

It's exactly that, you should find it

image.jpeg

If that's accurate... I might have to give it a go. (or is it iPhone only?)

Share this post


Link to post
Share on other sites

Is 5.5 NELM really 19.7 SQM and are they always directly convertible?  Not sure I trust the app for accuracy, though my eyes may be less trustworthy of actual NELM:  though I could make out a 5.5 averted last night, I couldn't make out the Daytime Double of the Panhandle.

(Confused!)

Edited by Special K

Share this post


Link to post
Share on other sites
2 hours ago, pipnina said:

If that's accurate... I might have to give it a go. (or is it iPhone only?)

Not sure if there is an Android version Pip.

Share this post


Link to post
Share on other sites
1 hour ago, Special K said:

Is 5.5 NELM really 19.7 SQM and are they always directly convertible?  Not sure I trust the app for accuracy, though my eyes may be less trustworthy of actual NELM:  though I could make out a 5.5 averted last night, I couldn't make out the Daytime Double of the Panhandle.

(Confused!)

I think the conversion is more an approximation than a direct one but I'm sure Acey can put me right on that! ??

I think the app is roughly accurate and can be used as an indication only. I took two readings last night, one showed 19.5, the other 19.2. My SQM-L consistently showed around 19.1 +/- 0.05. I think the dark calibration is key to making it as accurate as possible. Putting your finger over the camera is a little variable probably.

  • Like 1

Share this post


Link to post
Share on other sites
4 minutes ago, Stu said:

Not sure if there is an Android version Pip.

I just googled it, came up with this on their website:

y9fJsG3.png

I guess that's a resounding "No"

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.