Telescope Economics: To Build or To Buy?

Sam and scope

I built my 12.75-inch Dob for less than $700 — much less than a comparable commercially made scope would have cost. But is making your own scope always a money saving proposition? That's what inquireing minds (canine or otherwise) want to know.

For diehard ATMs, building telescopes is a way of life. But for others, the decision about whether or not to make a scope often hinges on economics. Will I save money building my own? The question shows up regularly in on-line forums and in my e-mail box. Before the emergence of a large-scale commercial telescope industry, the answer was a definite “yes!” But with the current abundance of low-cost, imported Dobs, and the increasing expense (and scarcity) of telescope-making supplies, it’s reasonable to wonder if it’s still possible to save a few bucks by going the home-made route. The prevailing conventional wisdom says “no,” but my own experiences suggest the answer isn’t as cut and dried as that.

To get to the bottom of the matter, I scoured the astronomy marketplace and gathered every scrap of pricing information I could find. I costed out mirror blanks and mirror-making kits, secondary mirrors, focusers and finders, plywood, aluminizing services, and so on, to assemble a set of data that was as accurate and up-to-date as possible. I also surveyed the current commercial telescope market to find the going rates for Dobsonian telescopes. The distillation of that research is presented in the graphs shown here.

Graph #1

As the data make clear, the build-or-buy question can’t be answered with a simple yes or no. Look at the plots in the graph above, showing the costs of purchased Dobsonians (yellow line) versus ones made by grinding your own mirror (green line). The two lines track closely across a range of apertures, with store-bought coming out slightly cheaper than home-built in smaller sizes. But an interesting thing happens when we move up to a 12-inch scope — the two lines cross, and then begin to diverge by increasingly greater amounts. Therein lies the answer to the question posed at the start of this article: yes, you can save money by making your own Dobsonian, but probably only if you attempt an instrument bigger than 12-inches aperture. But this tidy summary is only the big-picture perspective — some interesting information hides in the details.

One conspicuous feature of the graphs is the sudden upward spike in the price of manufactured scopes. This reflects the bi-modal nature of the current telescope market. Essentially, commercial Dobsonians are either imported, low-cost, mass-produced units (which mostly have apertures 12-inches and under), or low-volume, domestic instruments with bigger price tags. Were it not for the made-in-China scopes, building your own would be a money saver pretty much across the board. The graph below illustrates this point effectively. It shows the situation for smallers scopes — the market sector dominated by low-cost, imported instruments. Even making your optics does little to save you money in this size.

Graph #2

Another piece of information graphically presented is that it’s much tougher to save money if you skip grinding your own mirror in favor of buying one ready made (blue line). Indeed, doing so will generally mean spending considerably more than simply purchasing a finished instrument. Again though, once the aperture gets above a certain threshold, even this option becomes viable, but it never matches the savings realized by making your own mirror.

Before you make your build-or-buy decision though, keep in mind that this analysis is necessarily built upon averages and assumptions. As such, the graphs mostly illustrate broad trends. A great deal depends on the specific choices you make. For example, you can change the cost of building your own scope significantly simply by opting for an expensive focuser instead of a budget model, or by selecting a premium diagonal mirror in place of a more economical one. Similarly, as anyone who peruses equipment advertisements knows, there is a considerable range of prices and options among commercial scopes. In other words, once you decide on a specific aperture, you still have to do your research and apply your own selection criteria to what’s available.

One additional item the graphs don’t show is that of the three approaches, the build-it-yourself route offers the greatest potential for saving money. Commercial scopes are, more or less, an all-or-nothing proposition — you usually buy the scope as it comes. When you make your own, however, you can do a good deal of scrounging and opportunistic purchasing. It’s often possible for a group to buy ATM supplies in bulk to save money, and it’s not uncommon for club member to have extra parts they’re willing to sell for cheap. You can also defer some purchases for later. For example, you might start off by equipping your scope with an inexpensive focuser, and then upgrade later as money allows. Keep this in mind when tracing the all-DIY line on the graph — it’s probably the fuzziest one of all.

At the end of the day, however, making your own telescope isn’t purely a decision about economics. I feel the knowledge you gain from the experience, and the potential for customization, are two of the best reasons to give it a try — a telescope you make yourself really and truly is yours. And there’s no denying the pleasure in being able to say, “yes, I built it myself — mirror included!” I think most ATMs would agree, that’s priceless.

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Note: This article is an expanded version of one that orginally appeared in Sky&Telescope magazine.