Here's a little calculator for figuring limiting magnitude under different conditions with different size telescopes. Put in refractor for binoculars and convert objective size to inches by dividing by 2.5
http://www.go.ednet.ns.ca/~larry/astro/maglimit.html
It's fun to play around with that calculator, but I'm not sure that I really trust it's output entirely. For instance, I wanted to see how things would deteriorate as I aged, so I entered values for 20x80 binoculars, mag 5.5 skies, refractor, intermediate skill level etc. and then only changed the age variable by adding 5 years over the course of several decades. It actually had the limiting magnitude *increasing* with increased age. In fact, it had a 15yr old intermediate skill level seeing less than a 55yr old intermediate skill level. I repeated that with 20x100, 25x100 and 40x100 optics and watched what it computed. It claims 11.83 for 25x100 & 12.45 for 40x100 at mag. 5.5 skies, 35* from zenith. I think that's optimistic, at best.
As far as figuring out what seeing condition limiting magnitude to enter, here are a couple sites. Neither is particularly great.
North American Meteor Network:
http://www.namnmeteors.org/lm_calc.html
SEDS:
http://www.seds.org/billa/lm/rjm.html
Those can sugest areas of the sky to look at to see what you can see. I don't really like the fact that the SEDS one has areas defined by triangles. It's kind of tough to visualize the triangles artificially drawn beside a constellation to count stars held within. If you type "limiting magnitude" or "telescope limiting magnitude" into Google or Dogpile it's kind of amusing seeing what all comes back. Of course, the fact that I find it amusing may have more to do with the fact that it's 4:30am and I have NO sky to look at,(again), so I'm stuck with computer constructs.
Mike Swaim
http://www.go.ednet.ns.ca/~larry/astro/maglimit.html
It's fun to play around with that calculator, but I'm not sure that I really trust it's output entirely. For instance, I wanted to see how things would deteriorate as I aged, so I entered values for 20x80 binoculars, mag 5.5 skies, refractor, intermediate skill level etc. and then only changed the age variable by adding 5 years over the course of several decades. It actually had the limiting magnitude *increasing* with increased age. In fact, it had a 15yr old intermediate skill level seeing less than a 55yr old intermediate skill level. I repeated that with 20x100, 25x100 and 40x100 optics and watched what it computed. It claims 11.83 for 25x100 & 12.45 for 40x100 at mag. 5.5 skies, 35* from zenith. I think that's optimistic, at best.
As far as figuring out what seeing condition limiting magnitude to enter, here are a couple sites. Neither is particularly great.
North American Meteor Network:
http://www.namnmeteors.org/lm_calc.html
SEDS:
http://www.seds.org/billa/lm/rjm.html
Those can sugest areas of the sky to look at to see what you can see. I don't really like the fact that the SEDS one has areas defined by triangles. It's kind of tough to visualize the triangles artificially drawn beside a constellation to count stars held within. If you type "limiting magnitude" or "telescope limiting magnitude" into Google or Dogpile it's kind of amusing seeing what all comes back. Of course, the fact that I find it amusing may have more to do with the fact that it's 4:30am and I have NO sky to look at,(again), so I'm stuck with computer constructs.
Mike Swaim