Magnitudes

[Paboy46]

Hello everyone.  My question my question has to do with magnitudes. I'm a little confused, if a telescopes limited stellar magnitude is 14.2 I would be able to view any object under magnitude 14.2 on a clear night of course? I've been looking at online Messier objects and range from a 5 to 10.5 or higher or lower. So if a telescopes is 14.2 does that mean I could view them? Thank you

[Mognet]

Viewing an object depends on a lot of factors. The limiting magnitude is usually for ideal conditions. For DSOs the apparent magnitude doesn't always mean that the object is visible as it's the measure of the total light from the object. There's more about it here

 

[Stu]

As Mognet says, stars are point sources whereas other objects have an area dimension to them, so the light is spread out across this area. The concept is called surface brightness, basically how much brightness coming from a certain unit area.

So, the 14.2 tells you how faint you can see in terms of stars under ideal conditions. To work this out for deep sky objects is more complex. Globular clusters for instance are effectively made up from thousands of point sources, so do tend to cut through light pollution more than nebulae or galaxies.

Here are some links including some calculators which may help you.

https://en.m.wikipedia.org/wiki/Surface_brightness

http://www.users.on.net/~dbenn/ECMAScript/surface_brightness.html

http://www.unihedron.com/projects/darksky/NELM2BCalc.html

http://www.bbastrodesigns.com/VisualDetectionCalculator.htm

 

[chiltonstar]

Worth remembering too that the limiting magnitude is a statistical function (50%) for the average person: a more experienced observer can reach fainter magnitudes, given good conditions.

Chris

[Red Dwarfer]

8 minutes ago, chiltonstar said:

Worth remembering too that the limiting magnitude is a statistical function (50%) for the average person: a more experienced observer can reach fainter magnitudes, given good conditions.

Chris

I just read and screen capped that elsewhere - see the one ticked 

[domstar]

If your scope has a limit of 14.2 you'll definitely be able to see all the Messier objects with decent conditions. A 10 inch Newt has 13.8 according to astroshop (it has a great specs section), so you should be OK with ease.