Messier v Planets

[PJFan821]

A couple questions from a noob.

Im using: http://www.12dstring.me.uk/fov.htm to check some things out and Im wondering to myself:

1. What should appear larger on my Celestron 114 EQ, Planets or some of the easier to find objects in the Messier Catalog?

2. And why would planets seem small (size of a pin dot) compared to Messier objects that are huge according to the website when the planets are so much closer?

Any help would be great. Once the skies clear I want to start the Messier Marathon, but Im not sure if they will show up on my scope.

[virtualpilot45]

Messiers are usually bigger, with exceptions (eg M57). M42 is a nebula, but with hundreds of stars erupting into life from it, so it is incomprehensibly massive, and wait until you think about entire galaxies full of this stuff! It is therefore much bigger than say, Jupiter in a scope.

[PJFan821]

How easy is it to find the Messiers in suburban lighting?

[pete_l]

A couple questions from a noob.

Im using: http://www.12dstring.me.uk/fov.htm to check some things out and Im wondering to myself:

1. What should appear larger on my Celestron 114 EQ, Planets or some of the easier to find objects in the Messier Catalog?

Generally the M objects will appear larger - though not as large as comets can be. They are also much dimmer than the 4 "basic" planets (and the Moon) are, so are harder to see - especially in an urban night sky.

2. And why would planets seem small (size of a pin dot) compared to Messier objects that are huge according to the website when the planets are so much closer?

M objects contain a great deal more matter than a planet does, even though the planets are so much closer. That matter is also more dispersed: either in the gaseous M objects, or in the star-cluster ones. Planets on the other hand, are much denser - even than stars.

Any help would be great. Once the skies clear I want to start the Messier Marathon, but Im not sure if they will show up on my scope.

If you're in the UK you won't be able to complete the traditional Messier Marathon as that requires all the objects are eyeballed in a single night. We're too far north for all the objects to be above the horizon at some point in any given night. Although I've never tried it myself, I'm told it's also quite hard and since you're hopping from object to object it's more a study in ticking off targets than in enjoying the view.

Personally I'd take a more relaxed approad - which if you're planning to start now sounds like your idea, too. Also don't forget that there are a load of other DSOs that aren't M objects but are still worth a look.

[umadog]

How big something appears depends, obviously, on how far away it is and how big it actually is. The planets are closer, yes, but they are much smaller in reality than any DSO you will see. Jupiter, for instance has a diameter of about 140,000 km. It takes light half a second to cross that distance, so it is 0.5 light seconds in diameter. The Orion Nebula, on the other hand, is 12 light years across. That's a LOT bigger: three quarter of a billion times larger in diameter! I'll leave it to you to google the distance between these objects and the Earth. Divide the size of each object by its distance and you'll see why the Orion Nebula appears larger to us than Jupiter. Obviously size of the nebula alone is not sufficient to tell you whether it will appear bigger at the eyepiece.

Every DSO you see is vast! Most galaxies appear tiny, smaller than Jupiter, say, despite containing billions of stars. However, these tiny smudges will be tens of millions of light years away. You can do the same distance and diameter dividing trick and show yourself why they appear so small.

You can probably find most or almost all of the Messier objects from a suburban location. But there are bright suburban locations and darker ones. The suburbs of London, for instance, are generally pretty awful. You can use software (Stellarium) or a star atlas to determine the faintest star you can see near the zenith (straight overhead). If you can see magnitude 5 stars or fainter then you're doing pretty well. I have a fairly successful night recently under magnitude 4.5 skies. You can use the constellations Lyra and Cygnus at this time of year. People also use the little dipper, as it's always visible. Later in the night you could count the number of visible stars in the square of pegasus. Check out this thread:

http://stargazerslounge.com/observing-discussion/119565-how-determine-limiting-magnitude.html

Your best bet would be to get hold of a suitable book. I like Turn Left at Orion. It tells you how to find the brighter DSOs under suburban skies with a small telescope.