How much you can see with a telescope has everything to do with the size of your aperture. Smaller telescopes (4 inches and under) will not reveal very much in the way of nebulas and galaxies. That being said, bear in mind that somewhere between 1750 - 1800, Charles Messier compiled a list of approximately 100 diffuse objects now known as the Messier Catalog. These objects were difficult to distinguish from comets through the telescopes of the day. So don't write off that small scope.
The chart below will give you a good approximation of the effect that aperture has relative to how much can be seen. I have used stars to demonstrate the increase in visible objects and have listed the naked eye for reference. Limiting Magnitude refers to the faintest object visible with a given size of aperture. Please bear in mind that this number is also affected by local seeing conditions, the quality of the telescope and eyepiece's optics as well as the eye of the observer. More information on magnitude can be found in the glossary.
Do Not worry about Magnitude, i will come to this topic later. Just see the chart and get to know what is written below:
Aperture
inches |
Aperture
mm |
Limiting
Magnitude |
Number of
Visible Stars |
Naked eye
|
Naked eye
|
6 (maximum)
|
approx 8,500
|
4
|
102
|
13
|
approx 15 million
|
6
|
152
|
13.5
|
approx 30 million
|
8
|
203
|
14
|
approx 45 million
|
10
|
254
|
14.5
|
approx 85 million
|
12.5
|
318
|
15
|
approx 130 million
|
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