Rule number one when buying a telescope is to avoid department and discount stores. There are a lot of cheap telescopes out there. You get what you pay for!
There are three kinds of telescopes. There are the classic refractor telescopes where light comes in one end, and you look through the other end. There's also Schmidt Cassegrain telescopes, which tend to be more expensive but are more portable and are more suited for celestial photography. In general, I believe Dobsonian Reflector scopes are the easiest to use, and I think you can get the best bang for your buck. Dobsonians are suitable for all ages starting from about age eight and are so easy to use. Dobsonians are specially mounted Newtonian reflector telescopes. By the way, Newtonian reflector telescope was invented by who else, Sir Isaac Newton in the 17th century.
Newtonians collect light with a primary parabolic concave mirror in the back of the scope and reflects the image to a secondary mirror at the opposite end of the telescope. The secondary mirror angles the image to an eyepiece mounted on the side of the scope where you can magnify and focus the image. Different eyepieces provide higher or lower magnified images with the usual range being about 60 power (60 times larger than your naked eye) to over 300 power.
While magnification is important light gathering ability is more important. Light gathering allows you to be able to see objects to faint to be seen with the naked eye. Galileo said it best; telescopes "reveal the invisible." The more light you can gather into your scope, the sharper the image will be. Higher light-gathering capability is especially important if you're using higher magnification eyepieces. Light gathering in a Newtonian depends on the diameter of the primary parabolic mirror. Mirror diameters can be anywhere from three inches for young kids to over thirty inches for fanatics! Light gathering power increases by the square of the mirror diameter.
Another recommendation I have is to purchase a Telrad Finder to go along with the sighting scope provided with any telescope. It makes locating objects so much easier! You can buy one for under $40 at https://www.highpointscientific.com
By the way, I'm often asked if celestial photography can be accomplished through a Dobsonian. The short answer is…not much. Celestial photography is very complicated. Cameras needed are expensive, and your telescope needs to track stars across the sky. Even motorized Go-To Dobs come up short. Schmidt Cassegrain telescopes are better for deep space celestial imaging because they have enhanced motor drives and software.
It's possible to do some limited photography with a Dobsonian telescope, even with your cell phone. The biggest challenge is holding your phone up to your eyepiece and keeping it steady. Orion telescopes has a great device that'll hold your cell phone for about $100. It's called The Orion SteadyPix EZ Smartphone Telescope Photo Adapter.
Here are my specific recommendations.
1. The Celestron First Scope, designed for kids about 8 to 10 years old. It's not a pure Dobsonian scope but it's similar with a small mirror.... $55-$75
2. Orion SkyQuest XT8 Classic Dobsonian Scope.... For Teens through adult... It has an 8-inch diameter mirror....$400
3.Orion SkyQuest XT10i IntelliScope Dobsonian Telescope... An excellent adult scope with a 10-inch wide mirror. It comes with a small computer that will help you locate hard to find celestial objects... $899.99.
4. Celestron NexStar 6SE: This is a Schmidt-Cassegrain telescope and has a fully automated GoTo mount with a database of 40,000 plus celestial objects automatically locates and tracks objects for you. Just type in the astronomical target you want to see, and it'll electronically slew the telescope right to it and then track across the sky! I have this scope and love it. You can find out more at http://www.celestron.com. You can order it through Celestron but I recommend ordering through Starizona in Tucson, AZ. Their website is http://www.starizona.com....$800
If you're at all interested in serious deep space astrophotography, you need this scope. Starizona in Tucson, Arizona, has invented what they call a Hyperstar lens can be fitted onto most Schmidt-Cassegrain scopes like Celestron Nexstar 6SE. With Hyperstar, you can take fantastic images in less than a few minutes! Check out http://www.starizona.com to find out more about Hyperstar. The folks at Starizona are so friendly and helpful. They're the best!
5. Orion SkyQuest XX12g GoTo Truss Tube Dobsonian Telescope. This is an advanced Dobsonian scope with a 12-inch wide mirror. The has a motorized computer drive that will automatically slew your telescope to over 42,000 celestial objects and follow them across the sky...$2100.00.