Elan Valley Dark Skies Event 08-03-14

[laser_jock99]

Hi Mike,

Re the Elan Valley's SQM readings,

We've taken a number of readings at eight locations across the Elan Estate, and are planning to make a wider survey across the region for the Dark skies application - work in progress. 

The readings so far from the eight primary sites, vary from 21.18 to 22.80 - that equates to a NELM value of 6.22 to 6.95 

Regards,

Les.

PS -  Thanks for the name dropping Beulah.   Cheques in the post!

Those SQM readings seem to tally up well with mine (about 20 miles due North of EV) where the average moonless clear night reading is 21.85 and darkest night (i.e. cloudy) of 22.69 

[Mike73]

Those SQM readings seem to tally up well with mine (about 20 miles due North of EV) where the average moonless clear night reading is 21.85 and darkest night (i.e. cloudy) of 22.69 

Ah now this makes sense, I couldnt understand how Les's readings were so different! I was all but ready to sell up and move to mid Wales!! 21.85 is still very good though.

[faulksy]

have you ever taken readings in the claerwen area ? i have been down there a few times and its the darkest , blackest skys i have ever seen, and what about the usk area ?. thanks

[Wyvern]

Faulksy.

Interestingly the darkest (highest SQM reading) of 22.80 WAS at the Claerwen Dam picnic site. This reading was taken by Sorcha Lewis and at the moment, I don't know is this was a clear or overcast sky reading.

All readings that I've taken are clear sky readings.

All the best,

Les

[laser_jock99]

Faulksy.

Interestingly the darkest (highest SQM reading) of 22.80 WAS at the Claerwen Dam picnic site. This reading was taken by Sorcha Lewis and at the moment, I don't know is this was a clear or overcast sky reading.

All readings that I've taken are clear sky readings.

All the best,

Les

All the SQM readings I taken so far have had the Milky Way almost directly overhead. A bit like pointing directly at brightly lit cloud! There is more to taking SQM readings than might be imagined- in some ways SQM readings on cloudy nights could give a more accurate reading of local  Light Pollution than clear nights. What you are reading then is nearby lights reflected from the underside of clouds as opposed to looking at the relatively bright Milky Way for instance. It's a measurement that needs more study/qualification than I initially thought.  

[faulksy]

Faulksy.

Interestingly the darkest (highest SQM reading) of 22.80 WAS at the Claerwen Dam picnic site. This reading was taken by Sorcha Lewis and at the moment, I don't know is this was a clear or overcast sky reading.

All readings that I've taken are clear sky readings.

All the best,

Les

thank you les, the dam carpark was the first place i went to and was/is unreal darkness

All the SQM readings I taken so far have had the Milky Way almost directly overhead. A bit like pointing directly at brightly lit cloud! There is more to taking SQM readings than might be imagined- in some ways SQM readings on cloudy nights could give a more accurate reading of local  Light Pollution than clear nights. What you are reading then is nearby lights reflected from the underside of clouds as opposed to looking at the relatively bright Milky Way for instance. It's a measurement that needs more study/qualification than I initially thought.  

that makes sense , cheers laser

[Mike73]

All the SQM readings I taken so far have had the Milky Way almost directly overhead. A bit like pointing directly at brightly lit cloud! There is more to taking SQM readings than might be imagined- in some ways SQM readings on cloudy nights could give a more accurate reading of local  Light Pollution than clear nights. What you are reading then is nearby lights reflected from the underside of clouds as opposed to looking at the relatively bright Milky Way for instance. It's a measurement that needs more study/qualification than I initially thought.  

September can be a problem for getting SQM readings with the MW so bright at the zenith, I usually get readings of around 21MPSAS with Cygnus overhead but I take that as a false reading to be honest and prefer to aim just off the MW take three readings and average them.

This probably isnt the 'correct' way but I figure that as long as do the same every time those meter readings will be fairly accurate for myself anyway. Obviously not everyone uses the same technique as I do though but I think its more important to record a realistic reading than the first one we take (which is usually the best).

I travel a fair bit to get to the darkest skies possible so over the two years I've had my SQM meter its easily payed for itself in saved fuel easily. Its still my best astro accessory I've bought.