Massed Produced Mirrors

In recent months I have tested a signifcant number of production mirrors from inexpensive newtonian / dobsonian telecopes. I've examined at least one mirror from most of the "big" sellers, all of the results being fairly similar. Generally good enough for an inexperienced buyer to not be dissapointed but definitly should be better.

I've posted an article on my web site discussing quality criteria and sample data from one of these mirrors I just examined and refigured.

http://www.WodenOptics.com/cloudy.html

I suppose this could lead to discussions regarding manufacturers claims and honesty in reporting optical surfaces. However, I think the inexpensive "starter" level optics do serve their purpose. Without inexpensive telescopes, many people would never enter the hobby and have the opportunity to develop the skills and desire to appreciate hand crafted performance instruments.

Well, that's my 1:30 am rant!!!

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Cary Chleborad
Woden Optics
www.WodenOptics.com

A question:

Were these mirrors randomly selected from the production line or were they mirrors that were sent to you by owners who were concerned the mirrors were not up to snuff?

jon

I just finished putting together a small 6" f/6.7 newt using an Orion mirror. This is the only telescope I have ever made for myself using a mirror I did not make myself. I am very satisfied with the performance of the scope and the figure on the mirror appears to be very good. I did not run any numbers on the foucault tester, just the total correction and appearance of the shadows. The figure was very smooth and the total correction was about 95%. The star images are nice pinpoints and I have split doubles down to 1 arc sec so far.
All in all, I could not complain, and the truth is, I could not make one at the same cost just factoring in the materials! I realize this is a small mirror, and the chances of getting a very good or better mirror at the larger sizes are reduced dramatically, but I have seen some good examples out there.

Walt

I hardly think your testing "at least one mirror from most of the 'big' sellers...." represents an accurate statistical sample that would justify your conclusions. Your comments seem self serving.

High quality mirrors are more expensive than lower quality mirrors and will always be so. Machines used to produce better mirrors are very expensive and still are not up to "hand crafted" quality, i.e., "hand crafted" by a skilled optician. Skilled workers always get paid more than unskilled workers.

Your solution of refiguring "production mirrors" is not the general solution to the problem of quality. After all, after paying for your services, a person could have bought a higher quality telescope/mirror in the first place. Better "process control" is the answer promulgated by a distinguished contributor to this forum. Better "quality control" advocates another.

The ultimate solution to drive better quality mirrors is for the consumer to reject telescopes/mirrors that do not meet vendors quality claims. Nothing gets a manufacturers attention like a significant number of returns.

Russ Schnitzer

Cary,
Nice going, it is a good thing to show what to expect from an inexpensive scope.
Some mirror will be better and some worse. You just don't know for sure. But if you buy an inexpensive scope for $699 and spend $400 to have it re figured and coated, it is still an inexpensive $1,000 scope. This is not bad for a 12.5" scope.
Floyd