Part One: General Principles for Choosing your first Telescope
Submitted: Wednesday, 7th December 2005 by Brian Nolan
I have no vested interest in any equipment I write about here. And I’m no expert, just a hobbyist, someone who has hung around long enough to know a few of the pitfalls. If I’m no longer a beginner, then I’m not far past it, even after several years. Everything I write here is only my opinion. Lots of people will disagree with me. Just read the forums.
Yes, that’s right, I’m a “hobbyist”. I wasn’t born dying to be an astronomer. I don’t have a calling, or even a passion. If occasionally I’m obsessive, it’s still just a hobby (which doesn’t mean I don’t spend way too much time and money on it).
You’re a beginner. This is your “toe-in-the-water” telescope. You like astronomy, like the idea of it at least, and you’ve decided to take your interest to the next level. But maybe you’re unsure. (Will you stay interested…?) The last thing you want to do is waste your money. It’s possible that your first scope might also be your last scope. What you’re hoping to buy is something you will actually use, something you will actually enjoy.
So much I assume, but there’s a lot I don’t know. Do you weigh 60 or 120 kg? Do you have a bad back, arthritis, a crook neck? Do you live in the city, in a flat, up three flights of stairs? Do you drive? If so, what sort of car? These are all important questions. When it comes to enthusiasm, nothing kills it quicker than bad ergonomics.
And what sort of temperament do you have? Are you easily frustrated? (Perhaps avoid getting an equatorial mount.) Are you technically minded? An artist, a perfectionist? Is form as important as function? Are you intimidated by anything electrical, or do you just love all those computerized gadgets and gizmos? Then again, maybe you’re simply a plain, unpretentious, “near enough is good enough” kind of guy/gal, someone who wants something to plonk and point, something that gets you star-gazing in under a minute.
By the way, do you have an interest in terrestrial observing (birdwatching, etc)? In that case you might want a portable refractor that can do double duty in daylight. And are you more likely to spend snatched minutes or long hours observing (short tube refractor vs truss dob or GEM mounted SCT)? Do you live in a climate where mirrors take hours to cool, or where the weather pattern will frequently curtail your observing sessions (perhaps steer away from a Maksutov-Cassegrain, then)? And then there’s that tiny question about what you might actually want to look at (longer focal lengths for planets and double stars, wide fields for open clusters and nebulae).
Oh, and finally, do you have any inkling where your interests might take you? (The expensive quicksand of astrophotography sucks in a lot of amateurs. But if you ask me, astrophotography is a totally different hobby. Do your research. Then decide whether you want to live rich or die poor…)
So by now it should be obvious that no one can tell you what telescope you should buy. It’s a very personal thing. Probably the most useful thing anyone can tell you is what’s wrong with the ones they’ve got. Trouble is, people seldom admit that they’ve wasted their money. Call it cognitive dissonance, call it pride, but whatever you call it, it means you’ll hardly ever hear the truth. There’s just too much invested. They have to remain fiercely loyal to whatever they’ve bought, no matter how bad it is.
So, why trust me? Because I own pretty much every beginner’s scope there is..
(Well, of course, you don’t have to trust me. But if you don’t, chances are I’ll see you at AA. That’s Astronomers Anonymous. “Hi, my name is Brian, and I own too many telescopes…”)
By rights, you’ve already joined an astronomy club, bought or downloaded a set of star charts, learnt to identify a few constellations, looked at the moon and a few clusters with your trusty (and preferably tripod mounted) 7x50 binoculars, tracked down some globulars and the odd Messier object, watched Jupiter’s waltzing moons, trawled the internet, and subscribed to an astronomy magazine. (If you haven’t checked “yes” to most of these, then I advise you to hold off buying a telescope.)
You should also have a reasonable grip on most of the terms in this article.
Hopefully you’ve also looked through someone else’s telescope. If not, I’d better let you in on a little secret: astronomy, especially visual astronomy, is largely a conceptual hobby. By which I mean, the stuff you see won’t look that much different to what you can see through binoculars. (The big exception here is the moon.) In general, it’s largely what you know about the stuff that you’re seeing that appeals to a lot of amateurs. Sure, you’ll see cloud bands on Jupiter, and eventually spot the Cassini division in Saturn’s rings, but stars will always look like tiny pin-points no matter how big a telescope you look through, and “bright” deep sky objects frequently look disappointingly dim to a beginner. Not only that, and despite all those gorgeous photos you see on the boxes, pretty much every deep space object you’ll ever see will appear monochrome, colourless. No beginner’s telescope is big enough to show colour, nor detail in another galaxy. If you’re lucky you’ll see a grey smudge. Sometimes you won’t even see that. (The problem isn’t the scope, it’s your eye. The human eye just isn’t sensitive enough in low light. Colour is reserved for planets and a few stars.)
No, it’s the knowledge that what you’re looking at is mind-bogglingly huge, or ancient, or impossibly far away, that lends excitement to the blur in the eyepiece. (When I first saw the brightest object in the universe, it also happened to be the faintest speck in the eyepiece. I had to use averted vision just to see it. The person I was with just couldn’t see it at all. Geez, I was rapt!)
So, to avoid disappointment, please, please, PLEASE look through someone else’s telescope before you part with your hard-earned cash. You might just decide that you’ve got something more important to spend it on.
But if you’re truly determined, then read on…
Judging a telescope: the sigh factor
Here is my personal mantra. (It’s not original, and it’s not quite a syllogism, but it’s close.)
And here’s my first piece of advice: if the thought of carrying, or setting up, or pointing, or looking through a particular telescope makes you sigh, then it means you’ve got the wrong telescope. Maybe you’ll have to get rid of it. At the very least, you will have to modify it until it no longer makes you sigh. (Whatever you do, don’t let some absolutist try and persuade you that you’re the one with the problem. Maintain your self-respect. If it suits them but it doesn’t suit you, then it’s the telescope that has the problem.)
Easiest to carry
Fairly obviously, that’s the one that weighs the least. Or is least bulky. Or perhaps comes apart into smaller pieces (provided you’re not carrying it long distances or up and down flights of stairs).
Easiest to set up
An alt/azimuth mounted refractor wins hands down. (Newtonians need to be collimated, and are slower to cool.)
And then there’s these electronic fork-mounted GOTOs. Dearer, of course, but still touted as fit for beginners. While there’s usually an alignment/initialization procedure to follow at the start of each session, it seldom takes more than a couple of minutes, and it is very simple to learn. (Be aware, though, that even my 4 inch mak-cass takes over an hour to cool down.)
Having said all this, the purists will tell you that precise polar alignment with a GEM isn’t as difficult as you might imagine, you just need to be patient. (It’s more fiddly than it is difficult.) And if you’re engaging in long observing sessions, and can set up before dark, or are interested in astrophotography (even though digicams and derotaters and imaging software have largely negated this argument), then there’s no reason why a beginner’s first telescope can’t be GEM mounted. (It’s just not what I would recommend. Definitely try one before you buy one.)
Easiest to point (Well, point and track, actually)
For pointing, I’d favour a dob or a GOTO, I guess. (If I have to choose between setting circles and star hopping, I’ll hop every time.) For a dob, I consider a 1x finder essential (e.g. Telrad)!
Problems? Well dobs suffer from “Dobson’s Hole” (difficulty pointing near zenith). And cheaper GOTO’s can be temperamental in the cold. They are also subject to “rubber banding” and various idiosyncratic motor faults (the mechanical components are surprisingly low quality). They also require training and calibration episodically if you’re to achieve really accurate gotos. And of course, they rely on electrical power. (Some people say that GOTOs prevent amateurs from learning the night sky. This is simply untrue: doing astronomy teaches you the night sky, no matter what instrument you use.) EQ mounts, on the other hand, just put your eyepiece in impossible positions!
For tracking, it depends on who you talk to. A dob with smooth bearings can be made to track very well, and people usually get pretty good at nudging it (and there are powered tracking platforms now — although they’re not cheap), but a smooth dob can also blow about in the wind. With an EQ mounted telescope you’re really set, and often you can motorize the RA drives on a GEM so that you don’t even have to touch the slow motion controls. A fork-mounted GOTO scope tracks automatically, and even with its narrow field of view I’ve found that, provided it is properly aligned before a session, I can leave my little ETX in the backyard for half an hour or so and come back to find the object still in the centre of the eyepiece. Not bad at all.
Easiest to look through
What I’m talking about here is the mount.
Sure, there’s minuscule eye relief, stovepipe-like fields of view, out-of-focus finders, bodgy objectives, miscollimated mirrors…
But what I’m really talking about here is the mount.
Oh, yeah, sure, there are twisted eyepiece positions with EQ mounts, or unreachable eyepieces buried deep between an ETX’s fork arms…
BUT WHAT I’M REALLY TALKING ABOUT HERE IS THE MOUNT!
Yes, I understand. You’ve come across thousands of articles criticizing the optics in a particular telescope, and nary a word that bemoans the mount. But that’s only because a wobbly tripod and an unstable mount have driven people out of the hobby long before they even know what their optics are like! People who stick around quickly learn the critical importance of a sturdy mount, and they never turn back, never even glance at an OTA that isn’t properly supported. A bad mount is a passion killer, and people who persevere with a bad mount are making a big mistake. They end up leaving the game, and miss out on all the fun. Or else they hang around and hate life. In my opinion, a middling-to-poor mount is worse than terrible optics. A below average eyepiece simply makes you appreciate a good Plossl, a stiff or jerky focuser simply makes you wish you had a Crayford, and a marred objective simply makes you yearn for an apochromatic. But a bad mount makes you want to kill yourself. It’s the single biggest reason why you’re likely to give up on astronomy. It’s really, really true: the mount is half the telescope.
You need a rock solid tripod and a mount with smooth motion controls. Or you need a reasonable dobsonian with good Teflon bearings. Or else an equatorial head that’s designed to hold a scope much heavier than the one you put on it. Whatever design of OTA you get, be 100% certain that you’ve got it properly mounted.
Have I made myself perfectly clear? Here, maybe you should read this bit again. No, better yet, write it on the bathroom mirror, or in big letters on the bedroom ceiling…
Continue reading Part 2 of this article, "What's Wrong with each of my Scopes"