Telescope Advice

Factual Questions
1

I need some telescope wisdom.

I’d like something that would allow us to see planets as something other than points of light and the moon with a fair amount of detail. A number of the telescopes I’ve seen have computerized pointing devices that help locate various objects and I think that would be a feature worth having. I think I could possibly come up with about $400 to spend, but I’m at a loss about the type of telescope I should be looking at or any other features that would be good to have. Any advice?

2

While you’re waiting for Dopers to respond,
go to google.com and search on

low budget planetary telescopes

I did precisely that and got a fair number of hits.
It’s a good place to start.

You might also want to get an issue of
a Astronomy magazine to check out the ads.

I wish you the very best.

3

Inexpensive scopes come with two main types of mounts, equitoral and azimuth-elevation which is becoming more common. The AZ-EL mounts look simpler but cannot track the rotation of the earth without computer control and most cannot be used for long exposure photography. The problem is that the camera would have to rotate while the scope is moving in two axes at once. Equatoral mounts may look ungainly, especially the German mounts, but can track earth movement with just a simple motor and can be used for photography. An equitoral mount only has to move at a constant speed in one axis. Some, but not all AZ-EL mounts can be placed on a latitude wedge which basically turns them into an equitoral mount. Both can be good for planet viewing but consider future use when you are shopping.

4

I would recommend you try to locate an astonomy club in your area and go to one of their observing parties. If you are polite and friendly, most members will let you look through their scopes and you can judge for yourself what sorts of images are within your budget and expectations. My money says one look through a 12" Dobsonian will have you rethinking the automatic pointing feature and deciding that your money is better spent on the optics. Also, if you join a local club, learning how to use your telescope (no matter which type you get) is much easier than going it alone.

5

I’ll weigh in with a dissenting opinion and suggest that at your price range you purchase a scope without a goto device. You don’t have that much to spend, so I would suggest you maximize the aperture you’re buying.

Frankly, there’s also the fact that learning the night sky by hand is a useful introduction to astronomy, and is actually quite fun. Picking out the planets and the major sights isn’t really that hard; I got the hang of it very quickly and I’m a total doofus.

A common and good choice for the beginner is a 6" or 8" Dobsonian scope, which gives you a lot of aperture for a small amount of money. here are some examples, with fairly typical U.S. prices, and you get a couple of basic eyepeices. If you invest another $50 you can get a Telrad, a device that makes sighting objects vastly easier. I’ve even seen 10" Dobsonians for $495, and that’s a lot of aperture for that price. A 10" scope will give you gorgeous views. Remember, the key is aperture.

A Dobsonian won’t find things for you, but you’ll get big aperture for a low price, enabling you to see good moon and planetary detail AND get solid views of deep sky objects like galaxies and nebulas. With an 8" Dobsonian you’ll see some detail on the surfaces of Jupiter, Saturn and Mars, plus you’ll be able to see Jupiter’s four large moon and Titan around Saturn, maybe even a few others. Neptune and Uranus are distinctly disks, albiet without detail. Many nebulas and galaxies will be visible in very good detail; the ever-popular Orion nebula is just exquisite in an 8" scope.

But if you’re set on a goto device, there’s stuff out there for a good price. You won’t get much aperture, but you can get name brands. Of course, you could go halfway and get a reflector on an EQ mount with a goto; it’ll cost a few more bucks, but maybe you wanna get the best of both worlds.

Try www.telescopes.com to do comparison pricing.

6

Damn computer ate my post! OK, here’s try #2.

Before you even think about buying a telescope, you need to do a lot more thinking first. Can you recognize any of the major constellations or bright stars? If you can’t, then you’re not really ready for a telescope yet; even those fancy computer-controlled scopes need to be aligned using a couple of bright stars before they’ll work. Will you be transporting the telescope in your car regularly, or just using it in the back yard? Where will you store the telescope? Will you have to carry it up or down stairs? How much weight are you willing to lift? (Be VERY conservative here - if the scope’s too heavy, you’ll quickly get tired of lugging it around and stop using it). How “bulky” can the scope be - could you cope with a 4-foot long (but lightweight) tube, or does the tube need to be more compact in order to fit in your car or your storage area? Are you a mechanically-inclined person who’s willing to tinker a bit with a scope to keep it working right, or are you someone who would be reluctant to fiddle with the mounting to improve it or to tweak the mirrors to keep them aligned properly?

Any telescope with a lens or mirror bigger than about 3" will show you the Moon and the major planets - but the bigger the lens/mirror, the more detail you’ll see. And the more light you’ll gather, too, which means you’ll be able to find fainter objects (eventually you’ll want to look at things besides the Moon and the planets, and that’s when light-gathering power will really begin to matter).

Be advised that $400 is not a lot of money when it comes to purchasing a telescope. With that budget you won’t be able to afford good optics AND a large lens/mirror AND a stable mount (very important!) AND fancy computerized controls. You’re going to have to decide which things you’re willing to trade off. Very inexpensive computer-controlled scopes are putting almost all of the money into the computer; the scopes themselves are small (which means you won’t see as much), the optics are often mediocre, and the build quallity of the scope and the mounting may be iffy (although some models are fine). If you can handle a bulky (but fairly lightweight) tube, you might want to consider Orion Telescope’s new Intelliscope Dobsonians. These scopes don’t have tracking motors, so you’ll have to push the tube to keep an object in the field of view. But they have a LOT more light-gathering power than any fully computer-controlled scope with a motorized mount that’s in your price range. And they can be outfitted with a hand controller that contains a computerized database (purchased separately) which will tell you which way to point the tube to find an object. Since the hand controller is purchased separately, you could buy the telescope now and the controller later after you’ve had a bit of time to save up some more money. (You don’t need a fancy computer control to find the Moon and the major planets - they are easy naked-eye targets!)

In addtion to the excellent advice and links the earlier posters supplied, I’d recommend checking out the Forums and Equipment Reviews at Cloudy Nights Telescope Reviews. There you’l be able to get opinions from people who’ve actually used the telescopes you might be considering. And go find a local astronomy club if you can, attend some star parties, and get some “hands-on” experience with different types of telescopes before you buy!

Hope this helps. Good luck picking out a nice scope!

7

As I said in a related thread (which you should check out):

And don’t forget, for $400.00, you can get a pretty fine pair of binoculars.

8

Thanks, everybody, for your advice! To give a little more background, I’ve used binoculars and thought I’d rather buy a telescope than another pair of binoculars at this point.

You’ve convinced me that aperture is what I should be trying to maximize, so I’ll dispense with the automatic tracking feature. Since I’ll be adjusting the telescope by hand, what sort of mounting would be best?

9

One additional previous thread link that was not mentioned before (or at least I didn’t see it) is this one:

I used that thread (as well as the others) to decide on what telescope to purchase recently. I settled on an 8" dobsonian from Orion:

http://www.telescope.com/shopping/product/detailmain.jsp?itemID=14855&itemType=PRODUCT&iMainCat=4&iSubCat=9&iProductID=14855

This scope also has a controller (as mentioned earlier inthis thread, I believe) that guides you to any object of your choosing - this is different from the GoTo feature in other scopes because the GoTo feature drives a set of motors that physical move the scope to the desired star. On the Dobsonian, you enter the desired star and it tells you how much YOU have to move the scope, showing the coordinates on the controller display, changing those coordinates until they read X:0, Y:0 and you’re aligned correctly.

The controller on my scope is backordered, but I’ve had the scope for about two weeks now, and that has given me thr opportunity (whenever the skies are clear - damned clouds!) to just stumble through the heavens. I think I chose the right scope. It’s sorta portable (barely - it’s cumbersome and heavy to lug around), but other than that and it’s general bulkiness, I think I made the right choice for me. YMMV, but that’s my two cents worth. As pointed out earlier, you can always order the scope for now, and buy the controller later when more cash becomes available.

10

cybersnark, I have a friend who has one of the 10" Orion scopes, and he has the hand controller now and says it works beautifully. When yours comes in, I think you’re going to be pleased!

Depending on where you’re storing your telescope and where you prefer to observe, you might consider putting it on a small wheeled platform or a hand-cart to make moving it less cumbersome. A lot of folks store large Dobs that way in their garages; when they want to observe, they just roll the scope out onto the driveway. Since the scope is already close to ambient temperature (unloess you have a heated or air-conditioned garage), the cool-down time for the optics is minimal; even a 16" Dob can become a ‘grab-n-go’ scope with this sort of setup!

11

The key features to look for in a mounting is stability and smoothness of movement. You don’t want a wiggly, jiggly mount! You also don’t want a mount that moves in erratic fits and jerks. Tap the telescope’s tube when you’re looking through the eyepiece and see how long it takes the vibrations to damp down! If it takes more than 2-3 seconds, the mount’s too wiggly. Try moving the scope and feeling whether there’s any binding or sticking, or alternatively if a slight tap sends the tube spinning around like a top! Either situation is undesirable; the scope should move freely but not TOO freely (or it will be buffeted about by every light breeze), and it should stop moving the instant you stop nudging it or adjusting the controls (whichever the case may be). Think “smooth and controllable” when assessing the movement of the mounting.

There are two basic types of mountings: equatorial and alt-azimuth. Either can work well if it’s well-constructed.

An equatorial mount has one axis of movement tilted to match the tilt of the Earth’s axis; if you align the mount so that axis is pointing to toward the celestial pole, you can easily drive the other axis (either with a manual slow-motion control or with a small motor) so that an object will stay in the center of the field of view while you observe it. The downside of equatorial mountings is that they can be cumbersome and it takes some practice to learn how to set them up and use them properly, and they’re more expensive than an alt-azimuth mounting (for the same size telescope). But some people find the easy tracking they provide worth the added expense.

Alt-azimuth mountings, like the name implies, move up-down and right-left. To keep an object in the field of view with one of these mounts means adjusting the position of the telescope in two directions instead of just one (and at a slightly different speed in each direction!). This isn’t as difficult to do as it sounds, IF the mount moves smoothly. Many alt-azimuth mountings used on small refractors and short-tube reflectors come with two manual slow-motion controls to make the adjustments easier. Typically, to observe with an alt-azimuth mount you put the object at the edge of the field of view, observe it as it drifts across the field, then use the slow-motion controls or nudge the telescope to re-position the object before it drifts completely out of view.

The telescope that will give you the most bang for your buck is a Dobsonian. This is a Newtonian reflector mounted on a low-to-the-ground alt-azimuth mounting: the overall appearance resembles a cannon. Because of the way the telescope is balanced over the mount, the whole assembly is inherently stable and relatively free of vibration problems. You adjust the position of the telescope by nudging it gently; a good Dobsonian mount moves easily when you touch it so it’s easy to adjust the telescope’s position.

If you get a Dobsonian and later decide you’d really rather have a mounting that tracks, you can buy special platforms to put the scope onto convert it into a type of crude equatorial mounting. They’ll keep an object in the scope’s field of view for about an hour before the platform has to be re-set. But those platforms are expensive; a good one will cost more than your scope! But it’s an option you can consider adding later if you find yourself doing a lot of observing at high powers and are getting tired of the “nudge-look-nudge” routine.

One nice thing about amateur astronomy is that an initial investment in good equipment pays off, because telescopes don’t wear out. It’s not a hobby that requires you to keep upgrading; instead, you can use your funds over the years to improve the usability of the equipment you already have, or if you’re happy with the setup you’ve got you can observe for years with no additional outlay of cash.