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Home > Articles > How To > Beginners > Twelve Points to Consider When Buying a Mirror/Telescope - By Carl Zambuto

Twelve Points to Consider When Buying a Mirror/Telescope - By Carl Zambuto
By Carl Zambuto - 6/3/2004


1. BELIEVE THE REPORTS, when many, many people are saying the same thing. Yes, I’m speaking of the online reports from individuals and reviewers when they do say something. They will not say everything, but they -will- say something, so listen to that something and listen to it carefully. And of course, consider the source; whether they have an agenda such as if they are a “troll”, or a competitor, and so on. But by and large, if 25 different people say the same thing about a product, it is probably true.

2. Find the product that elicits an EMOTIONAL RESPONSE. Is that not what we are doing here anyway? We are in this hobby for an experience. So listen to what the individuals and scope reviewers say about their emotions. If you get continual responses such as "when the seeing got good I couldn't -believe- what I was witnessing, it looked just like..." and they babble on and on, acting like very happy children. That’s an indicator you’re on the right track, and it could well be the product to buy. And one more point- Make sure its not just one individual who has that response (for obvious reasons). Again, in the spirit of point number one, make sure it is a more common reaction to the product.

3. Pay attention to what you are NOT HEARING. For example when a reviewer talks about a big telescope being "big", and "tall", and "shiny" and shows "big, bright views" and on and on without saying anything substantial, watch out. Did they address performance, and did they make specific observations? Did they compare it with others on the planets, did they talk about contrast? Pay attention to what they are -not- saying, that is, be certain to read between the lines. Look for the substance. If you don't find substance in the review be wary of using it as a sole indicator. If you are not hearing about performance other than a term such as "this scope rocks", I would take the review with some salt. Remember, in the end, you are looking for performance.

4. Pay attention to which companies are NOT GETTING PRESS and reviews on the online forums and review sites. In other words, which companies are people conspicuously SILENT about? Is the only report available on the product from the company itself? This is not an uncommon condition. Watch out, because that is a clue. If you have a particular manufacturer in mind, try to find performance reports on them from objective third parties. How many are there? Example, if the company says “We have a customer who says it's just as good as a Rozzumzumi and it's only half the price!” -Watch out. If you’re going to put stock in it, make sure the review is not only substantive, but also that there are more reports out there than claims made only by the company’s advertising.
5. When you do read a negative report, listen to it carefully as well. What are they saying, and what are they -not- saying? Are they complaining about THEORY, or are they complaining about PERFORMANCE? Again, pay attention to what they are saying, and make appropriate considerations for the subject matter discussed.

6. ADVERTISING. Uh-oh, here's an interesting one. Who is advertising? Who is not, and why not? How much are they spending? What are they saying in their ads? Do they talk about numbers? Do they talk about test methods? Do they talk about theory? Do they talk about performance? Do they talk about popularity and use general terms, or do they talk about specifics? Can they say a whole paragraph without saying anything? Do they make broad statements that sound real good at first listen, but in truth mean nothing? Do they disparage other people's product? If so, why? And what is their guarantee? Do they guarantee numbers, or do they guarantee performance? Do they guarantee customer satisfaction no matter what? Do they guarantee not to be outperformed? Which is it and why? I'll leave it at that.

7. Now here's another one to look at: long lines. I'm going to make a generality here, it may not include all cases but I think it is worth considering. If you want to find value, LOOK FOR A LINE. Yes, I mean a waiting list. This does not necessarily mean "the best" in every case because a product does not need to be the best to have VALUE. At the same time, the list of products with lines will often include the best, because it is always a value to somebody. I'm not saying that a product necessarily isn't a value if it doesn't have a line, what I'm saying is take special notice of those that do. Folks overall are not stupid. Look for where the lines are and go find out why the line has formed. Talk to the people in the line, if you can. You may learn a lot. I'll say it another way: Mediocrity is easier to come by than excellence.

8. Specifically concerning reflectors, CALL THE OPTICIANS. Don't write to them, because they may not want to write what they might be willing to say on the phone. Get them cornered on the phone and ask them what is going on in the big picture. Do that with enough of them and soon you will know more than any one of them.

9. Refiguring services. This is a sub-point to #8. Ask the opticians, "Whose mirrors are you refiguring?" You see, if all the companies you have listed are in the "extremely good to exceptional" category, then whose mirrors are they all refiguring? Many have refigure services, and I can tell you, they are providing that service. Make a list. Ask each one who does refigures, whose mirrors they are doing. They may not tell you, but if they do, you have gained some VERY valuable information. Pay attention to who did the refigure and what company's optic it was. Find out if one company or two or three are doing refiguring on one or two or many of the others. And of course if applicable, pay attention to who is NOT on the refigure list. That might be a clue.

10. VETERAN AMATEUR TESTERS. Now here's one for you- Go talk to the veteran amateur mirror makers who wield the knifedge. Yes, I mean the bench Foucault test. They are the "keepers of the secret". There are commercial companies who will say that ATM's (amateur telescope makers) are not qualified to make assessment of the quality of their optic. I SAY DIFFERENT. These "swordsmen of the knifedge" are around, and some of them make public postings. There are likely some on this forum, and generally they do not have an agenda. Those people cannot be lied to. In about 60 seconds they can make a good qualitative assessment of the overall quality of an optic on the bench. In another 1/2 hour they can tell you everything there is to know about it and whether it is a “dog”, mediocre, good, very good, or stunningly superb. One example, there is an individual who posted on SAA some time ago who has tested some 50 optics in the last 5 years. He named names and cited numbers. For those who read it they gained some very good information. Pay attention to individuals like that. Outside of veteran star testers who have evaluated thousands of scopes in the field (very rare individuals) these folks know the very most.

11. See for yourself at a star party by TESTING AT THE EYEPIECE. The best test is a performance test done side by side with a known high quality instrument. But what I want to mention here is the Ronchi grating. It is a valuable qualitative tool at the eyepiece for the reasonably seasoned user. It does not lie. Take out the eyepiece, point at a bright star and put in the grating. Look for very straight lines, lined up with the spider as a reference. Any departure from straight lines could mean trouble because it is not real sensitive when used this way. Then look at the end of the lines as they go over the edge of the mirror. If you see any hook whatsoever you have a turned edge. TDE is a very common problem which kills contrast right from the start, and is easy to spot with this method. For those who want more sensitivity, try using it with a 2.5x Barlow. I'm not going to get into specifics here, but it is worth studying for those who want to. The Ronchi grating can also be used at the radius of curvature of the mirror. In an instant, with a simple $5.00 grating and a light source you can see smoothness of correction, surface roughness, zones and turned edge. You can see all this at a glance, and you can do this with the mirror still in the telescope (Note, there is a long study on Ronchi tests on the Zambutomirrorgroup at Yahoo, performed by member participation).

12. LISTEN TO THE VETERANS. The way information is dispensed has changed in recent years, due to our online world. One thing that has happened is anyone and everyone who wants to have a voice, can. Folks with little or no credibility can get the same exposure as those who have much more, in many different forums or venues now available to the public. If someone wants to speak loud and long enough, they can cause a real stir, if desired. On top of that it seems that so often statements made are authoritative in nature, when true authority is patently absent. I see many statements made such as “this is because of that, and this is how it is, period” instead of, “in my personal experience, I observe this happening”. For those reasons it is wise when considering choices to also learn the opinion and advice of a veteran observer. There are many places to find comment online, in books, and in magazines from many whose authority is well established and well recognized. Listen to what those who have been around for a very long time have to say. Usually, what they say is going to be correct, or very close to it, because they have the experience to recognize what is what.

-Carl Zambuto



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