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I just got a 4.5" Newtonian reflector. The skies haven't been clear where I live lately so I've only been able to use it to see the moon and Jupiter (I was also able to see the Galilean moons). A friend of mine with a similar telescope says he can see Saturn with its rings and the phases of Venus with his telescope. I am wondering what else I can see with a telescope my size, specifically which Messier objects I can see with my telescope. I live in a suburban area near a small urban area and so light pollution is a concern but I have access to darker skies close by.

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Once I've seen Andromeda with a similar telescope: it looks like a cloud as (I think) the telescope is too small to see any structure. The sky was relatively dark. –  Francesco Montesano Dec 19 '13 at 8:26
    
A big part of the answer is - What latitude are you at? The Double Cluster in Perseus is an amazing site in a small wide field scope. –  asawyer Dec 19 '13 at 14:51
    
I am at 40.75$^\circ$ north. –  Joshua Dec 19 '13 at 16:39
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The aperture of your 4.5" telescope is one thing, it's also important what focal length you have. Is it a f/5 or rather a f/8? The f/8 would be suitable for viewing the Moon, Jupiter, Saturn, maybe even Mars and Venus. You can also buy a good solar filter, attach it in the front of the optical tube assembly, and view the sun. But be careful with that, and inform yourself beforehand! Your eyesight might be in danger otherwise. For the Moon it is advisable to buy a neutral grey filter, because it is also very, very bright.

As for the Messier objects: you can probably view the larger ones. The Ring nebula (M57) will be tough, because it is very small and faint. But open clusters, globular clusters and Andromeda's core will be possible. A few bright nebulas will also be possible, like M42 (Orion Nebula).

There is a good list of all Messier objects over at Astropixels. You should try objects of magnitude 4 or better, and that have a size of more than 5 arcminutes. Otherwise they may be too dim or small to find.

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My telescope is f/8. –  Joshua Dec 19 '13 at 16:42
    
Then you can definitely take on the planets, since you will have about a meter of focal length. You should Start out with a 10mm eyepiece, and later buy a Barlow lens, or better: buy a good 8mm or 5mm eyepiece. The last may be expensive or not very suitable anymore for your telescope, though. –  Arne Dec 19 '13 at 19:47
    
My telescope came with a 20mm and a 5mm eyepiece, as well as a Barlow lens, so I should be good to go. –  Joshua Dec 19 '13 at 23:09
    
When you say view larger Messier objects. Do you mean it'll be a white dot, or can you actually see details? –  Mathew Foscarini Feb 27 at 16:16
    
Large Messier objects like open clusters will show lots of stars. The Orion nebula will seem like a grey, cloudy patch. The core of the Andromeda galaxy will also be a cloudy patch. The large globular clusters like M13 will appear as lots of stars in a sphere. –  Arne Feb 28 at 8:25
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