The Telescope Thread

In My Humble Opinion
1

I thought I had asked a couple years ago about telescopes here, but I’ll be danged if I can find it.

I have a basic, cheapie toystore aisle telescope for my kids ( actually two, which cuts down the fighting, if you know what I mean.) and with the warm weather and all, want/wish to upgrade. Possibly for an Xmas in July present.

I know dick about telescopes.

But, I’ve been looking at Edmunds Scientific Astroscan which looks more storable and portable, with the added bonus of looking like some kind of urinal :smiley: .

And naturally, I like this which is now on sale Yay!.

Any hints and suggestions from Smurter Dopers Paging Bad Astronomer! is greatly welcome.

2

First piece of advice: Magnification is irrelevant. You can get whatever magnification you want just by putting in a different eyepiece. So don’t buy a scope based on the advertised magnification. For that matter, don’t buy any scope that makes a big deal of the magnification, since any telescope which advertises the magnifcation prominently is probably junk.

Second piece of advice: Bigger is better. A larger diameter aperature will improve everything about a telescope. A bigger telescope can both see fainter objects, and can show more detail. The only limiting factors on aperature are portability, ease of use, and the depth of your wallet.

Both of the telescopes you link are pretty good. The Astroscan is just about the simplest telescope you can get, and is correspondingly very easy to use: Just point and look. The main drawback to an Astroscan is that it has very little in the way of features, and there’s not much you can do to add them. An astroscan will never have any sort of drive, for instance, so you’ll have to keep adjusting it by hand if you want to stay on the same object.

The Meade you’re looking at, on the other hand, has tons of features, including a go-to drive. Once you set up the telescope (this mostly consists of manually pointing it at a few bright stars, so it can get its bearings), you can just choose an interesting sky object from a menu, and it’ll automatically slew to that position and track that object. But it’s also much smaller aperature than the Astroscan, for a somewhat greater cost. And most of the fancy features depend on having a source of power (a car battery would probably last you the better part of a night)

And unfortunately, I don’t think that Bad Astronomer hangs out here any more.

3

I have no illusion of being smurter than you, but anyway…

The big conundrum is whether to spend money on fancy computerized control and learn to use it, or learn to navigate the sky yourself. Computerized (“GOTO”) telescopes like the Meade ETX can work very well once set up properly. You select the object you want to observe, and the telescope points to it automatically. But you have to buy or charge your batteries, wire everything up, input all the requested info (time, time zone, latitude/longitude, etc) and go through an alignment procedure (point the scope at a few bright stars) every time you use the telescope. And of course all this electronics costs money, money you could be spending on better optics and more aperture. Most GOTO telescopes are completely unusable without battery power.

Or you can buy a telescope with no electronic control, like the Astroscan, and learn to find objects yourself. For bright planets it’s a no-brainer: just look through the finder and center the object. For dimmer objects it means looking at a star chart and pointing the telescope at where the object should be, based on a pattern of visible stars. Obviously, for the same money you get more aperture and better optics. The Astroscan is a 4-inch scope and gathers twice as much light as the ETX-70.

The Astroscan has been around for decades, and for good reason. It’s extremely simple to use and very compact. But if portability isn’t an issue, you might also consider a 6" Dobsonian such as the Orion XT6 or the Celestron Starhopper 6. They gather twice as much light as the Astroscan.

As for GOTO scopes, the ETX-70 is pretty good product. (By the way, the page you linked to has the wrong photo and some erroneous info. Here is the correct product info.) Another good product in this price range is the Celestron Nexstar 80GT - it has a somewhat larger aperture (80mm vs. 70mm).

Whatever you decide to get, remember that the location is far more important than telescope choice. Well, not if all you want to see are the Moon and bright planets, but if you want to see deep-sky objects (nebulae, galaxies, star clusters) a $200 telescope under a pitch-black rural sky shows far more than a $2000 scope from the middle of the city. And be sure to contact your local astronomy club, they should be more than happy to help you choose a telescope, or help you use the one you bought.

4

It’s my understanding that for the newer models, all you have to do is point it at two or three bright stars (it doesn’t even matter which ones), without specifying the time or location at all. And you should be able to point it manually, even without battery power. Not as easily as with the Astroscan or a Dobsonian, to be sure, but it should be possible.

I should have thought to mention looking up the local astronomy club (you can see if your state is listed here, or Google for astronomy club + the name of a nearby city). Such clubs generally have public observing sessions, as well (either after club meetings, or at a full-blown star party), where the members will be all too glad to show off their telescopes. This’ll give you and your kids a chance to judge what they can do with various models, and what they want.

But other than that, I think we’re pretty much in agreement.

5

You may find this (and a number of similar threads) of some interest.

6

Here is a good review of this telescope which contains good general info on what to look for in any telescope:

http://www.dansdata.com/astroscan.htm

7

High-end models don’t require you to input latitude and longitude, but that’s because they have built-in GPS receiers. The ETX-70 isn’t one of them. And the “point to any two/three stars in the sky” feature is only available on the Celestron CPC series (starts at $1900). On other models you need to specify which alignment star you’re pointing to, then point to them. Or the computer chooses alignment stars and does its best to point to them (based on compass and tilt sensors), but you still need to know which alignment stars it’s trying to use and center the correct ones.

It’s possible, but really difficult to use that way. Telescopes built for manual operation have either manual slow-motino controls or very smooth Teflon bearings. A GOTO telescope with the clamp disengaged has neither, and is very awkward to use.

Personally, I think the ideal compromise between a manual telescope and a GOTO scope is a Dobsonian with a DSC (digital setting circle). A DSC is a computer that helps you find objects - you’re still moving the telescope manually, but the computer tells you which way to move. You can turn off the computer when you don’t need it, and you still have a silky-smooth Dobsonian. Power consumption is minimal. Unfortunately there are very few low-cost products like this; the Orion Intelliscope is probably the cheapest, at $460 (including controller).