Andromeda is a circular smudge?

[Apple15pie]

Hi guys

Got the heritage 130p for Christmas and i'm pretty sure i know how to use it and everything and have seen Jupiter many times and recently started looking at Orion nebula, which is fantastic

Tonight i had a look at Andromeda galaxy, and once i found the hazy patch in the sky in the right place i thought it was something else! From what i had heard and seen in TLAO it should be and elongated fuzzy patch, but what i saw was circular. I had a look around to make sure i wasn't looking at the wrong thing, but soon realised that it was Andromeda. Although it was great to see something 2.5million light years away, i still felt slightly disappointed as it was the wrong shape. Does anyone have any idea why it was circular (looked more like a globular cluster)  instead of elongated?

Thanks 

Dan

[acey]

What you were seeing was the brightest central part of the galaxy. If the sky was darker you would see more of the outer part, making the the galaxy look much larger. Binoculars at a dark site (where the galaxy is an easy naked-eye object) are sufficient to show the very large size of M31.

Spiral galaxies like M31 consist of a central spherical bulge (rather like a giant globular cluster) surrounded by a flattened disc. At a light-polluted site you can often only see the bulge part of spiral galaxies, so if you want to see detail in galaxies you need to get to a dark site, since all the detail is in the disc.

Elliptical galaxies are rather like giant globular clusters (or to put it another way, spiral galaxies are a bit like ellipticals surrounded by a disc). But ellipticals have very little dust in them, compared with spirals, so more of their starlight gets to us, and they generally have higher surface brightness than spirals. So although ellipticals tend to show less detail, they are also often easier to see, and it can be interesting to see their varied outlines (from circular to oval).

M32 (the companion of M31) is an elliptical, and has high surface brightness: at low power (e.g. in binoculars) it can be mistaken for a star. M110, the other prominent companion of M31, is also classed as an elliptical, but unusually contains a lot more dust, and is of much lower surface brightness, making it a harder target.

[Apple15pie]

ah that explains a lot! the moon was quite bright tonight... If i looked on a moonless night would i get better results or is it just because the sky is too light anyway in london to see the fainter bits of Andromeda without a bigger telescope? Thanks for the help though, i feel less disappointed with what i saw now

[ronin]

You need dark and a low magnification. M31 is 3 degrees across, assuming a plossl that means a magnification of 17x. So if you cannot get down to 17x you will not get all of M31 in view.

SGL Post on size of Andromeda.

That little thing to the left is the moon.

[timetraveler3]

Thanks, I have been wondering the same thing, now it makes sense!

Gary

[acey]

If you were viewing from London by moonlight then I'm impressed that you saw anything at all - just goes to show how bright the core of M31 is. At a heavily light-polluted site the presence or otherwise of the moon won't make a great difference, but if you can get to a site dark enough for the Milky Way to be visible (on a moonless night) then the galaxy will show its full glory.

M31 can be viewed at any power. In binoculars you get a sense of the whole thing, while a telescope enables finer details to be seen, such as star clusters within the galaxy. On all DSOs I just start low and work up. At a light polluted site it tends to be the case that only low power can be used on galaxies, as they got lost in the background when the power is racked up. At a dark site you can view galaxies at very high power - with my 12" I go up to x375. With that sort of aperture and magnification you can see globular clusters in M31 (though only one of them looks fuzzy, the rest are star-like).

I started another thread asking how close to London people could see the Milky Way - it appears there are sites within 20 miles.

http://stargazerslounge.com/topic/204329-milky-way-challenge/

It's important to note that for galaxies, you can't beat light pollution with aperture. If the disc of M31 isn't visible in binoculars then it will also be invisible in a 16" at the same site. Filters won't work either - the only way is to get a darker sky. You can't see galaxies in daytime, no matter how big a scope you use, and nor will you see them if the night sky is too bright.

[AndyWB]

Just to confirm what Acey and Ronin said - yes, that's just the very centre of Andromeda, and that's exactly what I see from town, in both the 130p and 250px. When I get out into the dark of the country, yes, it fills the eyepiece from one side to the other in the 130p. That's a 'wow!' moment you've to look forward to!