Rob I know what you are saying. It was 33 degrees out there which seemed quite hot because we were all out in the open, away from the trees obviously so we could get the best view of the horizon. It would have been murder if the temp got anywhere near the max it can get to out that way.
mostly cloudy last nite - couple of spots of rain in the late afternoon
no viewing last nite
overcast to-day so far
Glen, Allan and Rick are heading home this morning
Us more adventurous types are staying to see if it WILL actually rain
I mean, having brought the telescopes this far, it would be tragic if we didn't get the local farms some rain at least
For those interested, the Sky Quality Metre readings for Lake Chaffey on Monday night near midnight was 21.77 , the reading for Tuesday night near midnight was 21.55. No readings for the other nights due to the cloud.
Thanks for picking them up Arthur, I seem to forget them now and then, I appreciate it. I have bowls at home for him so there is no rush to get them back, hopefully at Bretti in the near future.
Average SQM readings I got throughout Tuesday/Wednesday session was 21.53. It's good to know our meters must be reasonably accurate seeing as we got almost the same readings.
For those interested, the Sky Quality Metre readings for Lake Chaffey on Monday night near midnight was 21.77 , the reading for Tuesday night near midnight was 21.56.
Quote:
Originally Posted by Allan
Average SQM readings I got throughout Tuesday/Wednesday session was 21.53.
Hey guys, a great night Tuesday, agreed! Trip was worth it for the viewing that night alone (not to mention the great company)
But what are some reference points on that scale? For example, do you have readings for some recent Pony Club nights, or Bretti, or Lostock?
What is considered good, bad and ugly?
On the significance of the measure magnitudes per square arcsecond:
....Now, the skyglow can be measured as the surface brightness of the sky i.e. how bright each square arcsecond of the sky appears.
This is what a Sky Quality Meter measures.
Roughly speaking, the surface brightness of the sky is ...
17 centre of a major city
18 high density suburb around city centre
19 outer suburbs with lower density population
20 low density fringe suburbs, uninhabited areas adjacent
21 rural area with a town in the distance
22 isolated location. Darkest sky possible.
....
but still interested in how those other site compared, and your own backyards?
Well I have got the wide version of the SQM so it takes a bigger sample of the whole sky, and the numbers run something like this. Anything above 21 is considered a dark site. At 22 and above it is a world class dark site. Measurements don't exceed 22 by very much anywhere on earth. Coonabarabran rates between 21.5 to 22.0, as the Milky Way is bright enough to affect readings when it is overhead.
So as you can see, Chaffey Dam is right up there. I haven't had my SQM long enough to measure the other sites, but that's what I bought it for. I have an inkling that Bretti will be a bit darker than Chaffey Dam. Lostock and Pony Club will surely be brighter, but will have to wait and see what the numbers say.
As Allan pointed out our two SQMs have different fields of view due to the lenses equipped, but as you can see from the figures reported at Chaffey it doesn't make much difference at a dark site. I regularly see readings over 20 in my backyard at Lake Macquarie but that is targeting the zenith again around midnight. To get an equivalent spread as Allan's lense I have to do a couple of spread readings. I did not have my SQM last time at Bretti but am lookng forward to the comparison. I was surprised by the Tamworth skyglow off to the low north-west at the Lake, but it did not seem to effect the viewing however I do believe Bretti maybe darker in similiar conditions because there is no town of significant in the area.
But 21.77 (from Monday night) is the darkest I have seen on my SQM - so far.
Here is a link to the Unihedron website that shows a comparison of the wide and narrow field lense:
I think from memory, Erick (presently in Haifa) brought his SQM along to the PC one time I was there. If memory serves me, the reading was in the low 20.xx range.
Maybe if Erick catches this thread, he can enlighten us more...
mostly cloudy last nite - couple of spots of rain in the late afternoon
no viewing last nite
overcast to-day so far
Glen, Allan and Rick are heading home this morning
Us more adventurous types are staying to see if it WILL actually rain
I mean, having brought the telescopes this far, it would be tragic if we didn't get the local farms some rain at least
geoff
I had a great time thanks to all the contributors especially Arthur for organising it.
This is my view of the sky!
Thanks for the update Geoff.
