Stellarium

[MartyB1973]

Hi,

I been using Stellarium to locate stars. Does Magnitude mean how light the object is, ie how well you can see it? If not is there anything out there that shows how bright objects are? I have a Skywatcher 127 SCT type, what light level is the maximum my scope can see. I look at objects via the Goto but think they are too faint to see.

[Bizibilder]

Magnitude is a measure of a stars apparent brightness as seen frm Earth (not the actual brightness of the star itself). A "bright" nighttime star maybe around magnitude 1 and most of the brighter stars that make up the basic shapes of the constellations are around mag 1 or 2. From a truly dark site, the naked eye may see stars down to about mag 5 or so.

A 127mm scope has a theoretical limit of around mag 12 - but in the real world, with light pollution etc you will not get very near that value!!

The Sun, being so bright, is mag -27 (minus 27) and the full moon -13.

Things like galaxies often appear much fainter than their given magnitude as the light is spread out over their surface and is not from a point source like a star - this can be a bit confusing when you start out as objects that you think you should be able to see are invisible!

As you learn your way around you will find that you can see more and more - simply due to experience when observing. Also, with faint objects, don't try and look for them if the Moon is about as its light can "wash out" fainter objects that can clearly be seen on a moonless night.

[MartyB1973]

Thanks, so the higher the number the fainter the object, wierd. Its been of great help.

[Naemeth]

Also, an apparent magnitude of 1 is 2.512 times the brightness of apparent magnitude 2. (So, apparent magnitude 10 is about 10,000 times fainter than magnitude 1, which is why so many stars appear so faint even with telescopes, they are so faint and so far away).

[Double Kick Drum]

Further to Naemeth's comments, surface brightness is also a useful guide. Where as magnitude indicates the overall light output of an object, surface brightness is a measure of how bright a DSO may appear.

Magnitude is fine as a light measurement where an object is stellar but for deep sky objects the light is spread over an area and so surface brightness comes into play.

An example of this is say M33, a galaxy in Triangulum which has a magnitude of 5.7. This would suggest it is easy to see but because the area of light emitted is quite large and spread out thinly it is actually challenging. By comparison M64, the Black Eye galaxy in Coma Berenices is rated at magnitude 8.5 but due to being smaller and therefore having a higher surface brightness, is much easier to see.

Once again, the lower the number the brighter an object is. SBs below 13 are usually tolerant of light polluted skies. Between 13 and 14, you will need a reasonable sky. Anything below 14 will need a pretty dark sky.

Hope that's clear!

[nipper]

Hi Marty, yes the magnitude scale can be a hard concept to grasp if you're not familiar with it.

As Roger et al have said it works in reverse.

0... 1... The brightest stars in the sky are 0 (zero) and then the scale "decreases"

2... 3... 4... most of the naked eye stars which make up the constellations and can be easily seen.

5... 6... Getting to the limit of the naked eye. From a really good dark site, 6 is about the limit for the naked eye.

7... 8... your average pair of binoculars or small scope will see these stars.

9... 10... getting really faint here. You'd be looking to see them with a 10-12" telescopes.

11... 12... 13... 14... very faint. Big scopes and dark skies needed here.

That's my quick 30-second introduction to magnitudes I gave to a small public gathering last month. It's not 100% perfect and only a very broad summary. I hope that helps.

[Viv]

Thanks Steve - will find that useful as well.

Here isn't a bad bit of info either

http://en.wikipedia.org/wiki/Magnitude_%28astronomy%29

[JamesF]

Just to illustrate how much what you can see depends on conditions, I was looking for M68 a few nights back in skies that are obviously fairly light at the moment because we're close to the summer solstice, but otherwise fairly free of light pollution. I could definitely pick out the mag 9.6 star about 20 arcseconds south and east of M68 with a sub-5" scope (my ST120).

James