Can LP be measured?

[blusky]

My measure is M53 is on the limit of the nebular/cluster light that I can see with an O3 filter. Which makes LP moderate?

[blusky]

Errrrm?

[hemihaggis]

My measure is M53 is on the limit of the nebular/cluster light that I can see with an O3 filter. Which makes LP moderate?

what ???? are you trying to say that M 53 is the faintest object you can see ?

do then mean to ask a question as to wether this makes the lp at your location moderate ?

????

[blusky]

And what's your opinion then? Most people find it difficult to see M1 at 8.4, so M53 at 8.33 is not a big surprise, is it?

[ollypenrice]

This is in a 200P? At a dark site M1 is visible in binoculars but using DS objects is not the way to measure limiting magnitude because surface brightness plays too big a role. Use stars.

The sky can also be measured using the Sky Quality Metre. It gives an indication of the ambient light. My site, which is mag 7 for young eyes, scores around 21.6 on an average clear night. You could get 22 in the Atacama, probably. (Never been!)

Olly

[umadog]

M53 is a globular so using an OIII filter on it would hurt not help. M53 has a bright core and M1 does not. This makes M53 a lot easier to see. The magnitude value is integrated over the whole object and assumes it to be uniform in brightness (which is never the case).

I find the Bortle scale to be useful: Bortle Dark-Sky Scale - Wikipedia, the free encyclopedia

On problem with estimating naked eye limiting magnitude is that different people come up with different answers. I suspect it's easier to get different individuals to agree on a Bortle value for a site. It's also fair to point out, though, that in some locations the sky quality can vary significantly in different directions. Last time I observed the NE looked like Bortle 7 and the SW looked like Bortle 5. Local light pollution will do that to you.