Opinion By Zane Landers
There’s a reason so many of the folks here at WAS use our fabulous 14″ EdgeHD telescope or have astrophotography rigs that took years to build up and master. While the idea of simply connecting a camera to your telescope and pushing a button is wonderful, it’s really not a realistic prospect. Astrophotography with a telescope requires a ton of gadgets, cables, and bits of expensive equipment that’s really too much for a beginner to handle – and especially not at a price point that can be measured in less than 4 digits.
If you’re planning on doing astrophotography or buying a gift for a photographer, consider a star tracker for a DSLR instead. A camera lens is really just a small telescope and you can get fantastic shots with a DSLR, tripod, and modestly expensive tracker – and it’s a great way to learn the basics of astrophotography such as polar alignment, exposure time, and image processing. Sure, it’s not as flashy and exciting as a “real telescope” – but a “real telescope” that causes frustration and gathers dust isn’t exciting either.
The #1 thing that people ask about telescopes is either how much magnification it has or how far you can see. Neither of these are actually particularly important features of a telescope. For one thing, telescopes don’t have a hard distance limit – you can see the Andromeda Galaxy 3 million light years away with the naked eye under dark enough skies, and an 8″ telescope can show you quasars billions of light years away. And magnification is limited by a few factors. For one thing, most of the far away things in the sky are faint – really faint. Magnifying them too much spreads out the image, making them dimmer and harder to see – as well as harder to locate and fit in the field of view. So even with very large telescopes, most viewing of deep-sky objects – stars, galaxies, nebulae etc. – is done at below 100x or even 50x if possible. You can of course change out eyepieces for different magnifications based on what you’re looking at and other factors, but finding most things and viewing maybe 50-75% of all things in the sky is generally done with the lowest possible magnifications one can use with a given scope.
The Moon and planets are quite bright, but the Earth’s atmosphere as well as the physical resolution of the telescope limit us here too. An 8″ telescope might be capable of 400x on a perfect night, but rarely will 400x reveal more detail than 300x or 200x or even 100x, and on a turbulent night like we usually get in New England anything above 200x with any telescope is going to be a mushy blob.
So steer clear of any telescope that advertises itself based on magnification – it’s almost certainly a marketing ploy designed to con you into buying a junk instrument.
For visual astronomy (that is, looking through it), the #1 factor in how much you can see is how good your skies are. Light pollution from cities will wash out faint objects and make them harder to see or invisible altogether. But the #2 factor is aperture. Aperture refers to the diameter of the mirror or lens that focuses the light in your telescope and is typically expressed in inches. Light gathering ability goes up with the square of the aperture, while resolution is linear. So an 8″ telescope will have twice the resolution of a 4″ telescope and 4 times the light gathering ability! This will let you see fainter objects as well as view brighter ones in more detail.
Typically telescopes are grouped into a few categories of size by aperture:
Small – 4-6 inches. A 6″ telescope is the smallest instrument you can buy that will really shine on deep-sky objects, below that it takes a bit more patience to see dim objects. The Moon and planets look stunning in even a small telescope, and any scope in this size category can be carried in one trip or even with one hand and fit in almost any vehicle or storage space. Telescopes of this size can use lenses (refractors), mirrors (reflectors) or a combination of both (catadioptrics). Refractors produce the sharpest views for their size but are impractical and expensive, catadioptrics are compact.
Medium – 8-12 inches. The best telescope for most people is in this category, and probably a reflector. A scope this size still fits in the trunk of a car, will show you thousands of interesting things and isn’t much of a chore to set up and use. The largest scopes in this category, 12″ reflectors, might fill up a smaller vehicle and can be a bit bulky, but still are easily managed by one person. A catadioptric scope is still an option at this size range but is starting to get expensive, while refractors are pretty much out.
Large – 13-22 inches. A telescope of this size is almost certainly going to be a reflector. Most scopes in this category are easily managed by one person with practice, but are often nearly as tall and heavy as you are and are composed of trusses rather than solid tubes, which have to be assembled. The views are worth it – but a beginner should probably stick with something smaller.
Very large – 22 inches or above. More often than not, these tend to be permanently set up or at least rather cumbersome to transport and put together. Scopes this size aren’t just telescope anymore – they’re a lifestyle choice – requiring ladders, loading ramps, and even custom trailers to accompany them on travels and with costs ranging upwards of 5 to 10 thousand dollars. Obviously we would skip out on this size for a beginner scope, even if you do have the funds.
The #1 type of telescope I would recommend for a beginner or indeed anyone is a Dobsonian telescope, preferably in the 6-12″ aperture range. This is a reflecting telescope on an alt-azimuth mount that moves like a cannon or a camera tripod. You swivel it left and right and aim up and down. There is no leveling, no alignment, etc. to be done – you just set it down and aim at what you want to look at. Occasionally you might need to line the mirrors up with each other, which takes a few minutes. When a target drifts out of the field of view, you gently nudge the telescope along to keep up once every minute or two. That is all.
Why? Isn’t a computerized telescope better? Aren’t refractors sharper? Isn’t an equatorial mount more professional or something?
In theory, yes. A computerized telescope will point at anything you want… after you level the tripod, align it with a set of reference stars, enter in the time, date, and location, and probably sync it on half a dozen more reference objects after the alignment when it inevitably doesn’t point where it’s supposed to. By the time you’ve learned to deal with all of that, you could probably have just gone ahead and learned the sky – there are always phone apps to help you nowadays. And an equatorial mount requires a dizzying process of balancing, polar alignment, and all sorts of other stuff. You’re more likely to end up with the telescope pointed at nothing, crashing into itself or some sort of other mishap than get a nice view of the Moon, or Saturn, or the Orion Nebula. And then there’s the cost aspect – those doodads and motors and counterweights and tripod legs are sucking up the money that would otherwise go into the splendid primary mirror that actually does all of the work of the telescope part.
If you decide later that you want to learn astrophotography, a computerized telescope and equatorial mount will be needed, yes. But learn how to use a telescope first and get something that’s simple, hassle-free and a good deal for the money – and worry about the more complicated stuff later.
As for why a reflector – apart from the cost aspect, refractors typically don’t come at sizes above 5-6 inches and are quite cumbersome and expensive at that size whereas a 5″ reflector fits in a backpack, while most commercial catadioptrics have increasingly small fields of view and end up being generally inconvenient as they get larger.