Volunteers needed for naked-eye sample (Full Moon)
Hi all,
Something you can do out there under a Full Moon. The imagination runs wild here!
I'm hoping to get a sample of naked-eye limiting magnitudes using the constellation Crux. In a few weeks, I'm going to re-sample near New Moon.
If you would like to participate. Tonight, or over the next few nights, could you simply note the magnitude of the faintest star you can see (naked-eye) from the attached map. I haven't shown all stars to magnitude 6. Somewhere between 7pm and midnight will be fine.
Then report two things back to this thread.
a) limiting magnitude b) whether it was an inner city, inner suburban, outer suburban or rural reading.
Thanks, Rob.
Last edited by Robh; 09-05-2009 at 10:56 PM.
Reason: Correction mu Cru 4.0
Guess I'm first.
Had to shield the Full Moon from view. Too distracting.
Could see mag 4.3 (mu Cru) with certainty and, off and on, the mag 4.6 star closer to it.
Live in an outer suburban area.
9pm
My husband Greg took part as well. We shielded our eyes from the moon, and we both agree that our limiting mag is 5.5.
Though I had to use averted vision and even then the star would pop in and out of view.
We live in a Rural area.
Had a go. Could see mu Cru easily, but I think it might be a bit brighter than the mag 4.3 you've got marked (mag 4.0). In any case, could see delta Cru at mag 4.3, and nearby zeta & eta Cru easily (4.0 & 4.1). Funnily enough, surprised that I could see the Jewel Box - also lambda Cru 4.6, right on the very limit & only popping into view occasionally. Nothing deeper.
So, limiting magnitude 4.6.
Rural setting (I live in a 'suburban' street in a country town say 3000 pop, but am right on the outer edge)
Could see mu Cru easily, but I think it might be a bit brighter than the mag 4.3 you've got marked (mag 4.0).
Rob_K, thanks for the correction on mu Cru at 4.0. Also Les.
Have corrected attachment. Hasn't affected any of the readings on earlier posts. Fingers crossed for anyone outside now.
Apologies, Rob
Only a small sample but looks like NELM (naked-eye limiting mag)
around 4.5 for outer suburban
up to 5.5 for rural
under a Full Moon.
Appreciate any further input tonight or tomorrow night, especially any observations for inner suburban or inner city. Will update again tomorrow if I get any more data.
At the Macquarie Uni open night I could not see anything dimmer than mag 2.8. (only three stars of the Crux.). The telescope area was bright enough to read the paper even after some of the floods were turned off.
Through a 10" LX200 the jewell box was there but looked awful flat. Omega Centauri was just visible and The Tarantula the central portion (about two arc minutes) was visible. Luckily most only wanted to see Saturn or the Moon.
Had another go tonight, just out of interest. Transparency was better with skies noticeably 'darker', more than could be accounted for by the slight phase change. End result no different, but lambda Cru and the other mag 4.6 star could be held better tonight.
I just went outside and had a bit of a squiz.
Only A, B and Ga were clearly visible at all. D and E became slightly visible after about 10 minutes of adjustment but nothing much else after that.
I live in the Inner city Sydney about 1.5k East of the CBD.
What was the deal with holding a public star party on the Full Moon ? I've never encountered such a thing. First quarter is a good idea though.
It is not actually a public viewing night. The telescopes are just an addition to a public astronomy lecture that is held twice a year (autumn and spring) and has more to do with available times at the university. It was just bad luck that this time was full moon, although this is the first time in about 20 years that that we have actually had a full moon. At least we had some clear sky fo a couple of hours. Better than rain or clouds.
Update for NELM.
Getting some idea of the rough ranges under a Full Moon:
inner city 3-3.5
inner suburban 3.5-4
outer suburban 4-4.5
rural 4.5-5.5
Will continue for another couple of nights as still near Full Moon.
If you would like to participate, grab the map below that now has some instructions.
The more data, the better I can gauge the moons effect on naked-eye limiting magnitude. I have a map ready with stars to mag 7 (Crux map 2) to repeat the test nearer New Moon, 19th to 25th May. Will post in new thread later.
Thanks to all contributors, Rob.
Last edited by Robh; 11-05-2009 at 08:42 PM.
Reason: Attached new file
