How dark? - estimating naked eye limiting magnitude?

[erick (Eric)]

Can someone give me some simple tests to get an estimate - probably a set of increasingly fainter stars/objects that are easy to "locate" and see or not see as the darkness permits.

I've looked at some detailed stuff:- http://www.imo.net/visual/major/observation/lm No, too much information

I read in an earlier thread, a few suggestions for some limits in quite dark conditions:- Eg. seeing NGC 2808 (a 6.2 mag glob) in Carina and seeing the one lone star (SAO252046, mag 6.5) within the Coal Sack Nebula.

How about a set of steps from, say, seeing four stars of Crux, down to objects around mag 6.5?

Why do I ask? I'm just about to move from big city suburbia to a country town whose population is about 10% of my current suburb only (but within ready access to the big smoke - job not changing)! A quick look suggests I might get in some good viewing from the backyard of my new place. I'd like to properly compare the difference.

Thanks in advance

[glenc (Glen)]

Eric, here is a SkyMapPro map of Crux at about 7pm showing stars to mag 7.

[erick (Eric)]

Thanks Glen, I'll work with that - we might be in clear(ish) skies tonight.

But, in truth, I need the "Estimation for Dummies" version. Eg:

1. Can you see Epsilon Crucis (marked "1" on reference map), then limiting magnitude is X

2. Can you see (a fainter object, but one whose location can be easily located - say half way between two bright stars) - marked 2. on map, then limiting magnitude is Y

3. Can you see etc.

I'm sure some of you guys have such a protocol in your heads. I'd think that many of us would benefit, not only me.

Cheers
Eric

[Ian Robinson]

I use the Pleiades as a guide in summer , I count the stars I can see with a dark adapted naked eye in the group.

In winter I judge it by how well defined the LMC and SMC are.

Yes - Very subjective.

[Terry B]

It seems to be very subjective. Depends if you use averted vision or look directly at the star. Both will give very different results. There is a nice article in the recent Astronomy mag about averted vision and limiting magnitude.

[goober (Doug)]

Some star atlases have limiting magnitude charts. Nortons and Herald-Bobroff off the top of my head.

[erick (Eric)]

Thanks Doug - searching "limiting magnitude chart" is very useful, eg: http://www.phys-astro.sonoma.edu/obs...magnitude.html

[erick (Eric)]

OK, here's the go! Star counting!

http://obs.nineplanets.org/lm/rjm.html

I'll try areas 26 and 27!

[jjjnettie (Jeanette)]

Good question!
Thanks for posting.