Lens recommendations for Canon DSLR?

I'm looking for a new lens for my Canon 70D that suits what I want.

I need- a lens that is a wider angle, under a 20mm, is great in low light (I'll be using it to take long exposures of the stars in the night sky), also a lens that is great for daytime landscape shots as well.

If anyone can please recommend a good lens that fits those requirements that isn't too pricey, please respond! It would be well appreciated!

I'm looking for a new lens for my Canon 70D that suits what I want.

I need- a lens that is a wider angle, under a 20mm, is great in low light (I'll be using it to take long exposures of the stars in the night sky), also a lens that is great for daytime landscape shots as well.

If anyone can please recommend a good lens that fits those requirements that isn't too pricey, please respond! It would be well appreciated! Thank you! Your 18-55 mm lens is fine for shooting the night sky.

Landscape photographers typically use a lens like the 10-18 mm if they have a Canon cropped frame camera

My colleagues who shoot with Nikon's use either a 12-24 mm (DX) or 14-24 mm (FX) lens when shooting architecture, landscapes and the night sky.

What is MOST important is making sure that use the noise reduction for long exposures in your cameras menu to On. This will help reduce the noise found in night sky when shooting long exposures. Remember, exposures longer than 30 seconds will require you to use some kind of motor mount to keep your camera aimed at the portion of sky you are shooting. The earth moves, so your camera must be in sync with that movement Yo're going to have to tell us what you consider "too pricey".

I'd suggest the 16-35 f/2.8, in either variation. Shooting stars will need at least 2 seconds. You don't need a fast lens. The 18mm end of the kit lens will do.

http://keerok-potd.blogspot.com/2012/02/polaris.html In theory wider is better. However, you could find that corner softness gets worse. That can be corrected by stopping down, but stopping down is something you want to avoid to get enough light.
An advantage of a prime lens is that if it has a distance scale (some pancake lenses don't) it can be more reliable for dialing to infinity than a zoom lens. Zoom lenses are usually not parfocal--i.e. Focus shifts with a change of focal length. Sigma 10-20mm is a superb lens. Try 10-20mm for night shots.

Yo're going to have to tell us what you consider "too pricey".

I'd suggest the 16-35 f/2.8, in either variation.

Shooting stars will need at least 2 seconds. You don't need a fast lens. The 18mm end of the kit lens will do.

http://keerok-potd.blogspot.com/2012/02/polaris.html

In theory wider is better. However, you could find that corner softness gets worse. That can be corrected by stopping down, but stopping down is something you want to avoid to get enough light.
An advantage of a prime lens is that if it has a distance scale (some pancake lenses don't) it can be more reliable for dialing to infinity than a zoom lens. Zoom lenses are usually not parfocal--i.e. Focus shifts with a change of focal length.

Sigma 10-20mm is a superb lens.

Try 10-20mm for night shots.