I'm considering getting myself a cheap telescope (e.g. Celestron Astromaster 90AZ or Celesteron Orion SkyQuest XT8) giving around 200 to 300 times magnification. I have a few questions:
- Is a Galilean or Newtonian telescope better for these purposes? My understanding is that Galilean telescopes create a rainbow around objects which Newtonian telescopes don't; Galilean telescopes are better for viewing objects in the solar system while Newtonian telescopes are better for viewing distant galaxies and nebulae. Is this correct?
- Are computerised telescopes worth it for an amateur beginner?
- Is it easy to find objects in the night sky? I presume the slightest movement of the telescope may change the location of your image by light years. And things move quite rapidly in the night sky so the telescope's position has to be changed all the time to keep the object in view.
- On websites like Gumtree I see telescopes offered for sale, "only used four times" etc. Is there a good chance that a telescope will become a piece of furniture that collects dust?
1. I'm more familiar with the terms refractor and reflecting telescopes. The more affordable refractors will show a slight purple or yellow fringe around bright objects. Higher end refractors (apochromatic) use exotic glass, triple lenses etc. that more or less eliminate any of these problems, but are very expensive. Reflectors (Newts) don't have this problem, but they do require regular collimation for best views.
The solar system vs deep sky thing is debatable. Both can do pretty well on all objects, based on various other considerations. But it is somewhat complicated to directly compare them -
read here. For feint deep sky objects aperture is king. The larger the aperture the more light it gathers and more details become visible in things like nebulae etc.
2. Depends. Do you want to learn to find objects for yourself? Would you have a way to power a computerised telescope? Do you have a large enough budget? They can be great, since you can just tell it to go to Mars, and automagically it goes there and you can look at it. It will also track the object. Downside is that you'll most likely never go to the trouble to actually learn the sky and for some that's half the fun and challenge.
3. Some objects are easy, others are extremely tough and frustrating. Moon, planets and bright nebulae can be easy to find with basic knowledge of the constellations using star hopping. Faint objects can be quite a challenge and learning the constellations can be tough to get to grips with. Are you actually looking at the right spot? It's daunting at first and gets easier with practice.
4. Yes. Depending on the size and complexity of the telescope they can become a chore to set up and you might lose interest as time goes by. I've hardly used my telescopes since a new house went up next to our backyard. Blocks most of the sky and constant light ruins the view.
Best advice is get a good pair of binoculars. Learn the constellations and see all the bright objects you can (binocs are good for star clusters etc.) If that keeps you interested you'll know you are ready for a telescope.
A 90mm refractor would make a nice first scope. It's easy to carry around and gives decent views of the planets and star clusters, although some viewing positions can be uncomfortable. If you stick with it after that you can move on to a larger scope such as the XT8 which should give you enough aperture to view most things for years to come.
