I would advise the purchase of a good quality 4.5" Newtonian Reflector to begin with. You get a larger aperture (wider mirror v lens) for your money, which will allow you to resolve more detail than a similarly priced refractor, typically an 80mm. Also the price of refractors increases dramatically the larger they get due to the difficulty and expense in making the biconvex lenses, whereas a reflector works by using a large concave mirror to gather the light, hence costing less to manufacture. Other types of teelscope do exist but most are double the cost and more, even for the lower range models, again due to the complexity in their production. There are advantages and disadvantages with each, which I have weighed out in the table below. Please note that you should try and buy a telescope with an equatorial mount, although more difficult to use than a dobsonian or alt-azimuth mount, it gives better control and will definitely be required for deep-sky astrophotography. This is because it can track an object accurately across the sky if motorized and set up correctly, which is necessary for lomng exposure shots. The increased control will also allow you to move between small objects more easily, for example, craters on the moon. With an alt-az, the slightest movement could put it wildly off course, which can be highly irritating when you are searching for something in particular.