Don

At this point I will defer to Dean the owner of Starizona but will add these comments.

Please allow me to pontificate.

First in order to replace the washer you will have to remove the corrector. It can be done with added difficulty by not removing the corrector but you could scratch the corrector coatings which is not a good thing to say the least. This is a task that should not be taken lightly. On the Edge as well as on other SCT models the corrector is centered, actually moved into position, in the scope front tube end ring and this is not always the exact center of the front tube ring hence the need for shimming, screws, etc, and alignment.

In the real world there is also a little matter of a thing called “coplanarity”. Everything you manufacture has a certain flatness and each plain has a certain ?alignment with regards to other ?plains on other components of an assembly. This applies to lenses surfaces and the surfaces to which lenses are mated with. Now you throw in a big aluminum tube with holes in the periphery which are aligned with holes in the end housings of the scopes. You see where this is going. This is why mounting rings etc. have to be twisted and turned so as to allow for the most perfect coplanarity of all components. Now you throw in “axial” alignment and you begin to see the complexity of optical systems. Not even say the secondary mirror back surface which is flat may be perpendicular to the focal point axis of the curved mirror so collimation takes care of this also.

Not all scopes are created equal. Sometimes in the manufacturing process or components or in assembly all the errors cancel out each other and you have a perfect scope. On other occasions you have the “combination” of errors working against you, this is what is known as a “lemon” and you get a fair scope. Yes they are still within the acceptable design criteria but not as good as the “Perfect” scope. It is just a matter of luck sometimes. Sometimes we play these errors against one another in an assembly to our advantage and it is done a lot.

In manufacturing there is a thing called Geometric Tolerancing. It is a method by which all parts are made so as alignment with other parts in complex assemblies will be insured. It is different than simple part print tolerancing and is necessary in complex assemblies.

In a perfect world everything would be flat, round, concentric, perfect in axial alignment, etc. and the list goes on. Optical alignment is a pesky thing.

In the early days corrector alignment was accomplished with cork shims, which eventually shrunk, and of course this was done on an optical bench, as they still do. The alignment of the corrector can be done to a degree, and I use the term degree in a comparative nature, by eye. This however in no way, compared with the alignment accuracy needed for astrophotography, is acceptable. This applies many times over for Edge Scopes. With the edge you are paying for as nearly as possible perfect optics and superior alignment. This is what you paid for. There is a white paper on the Edge scopes and it can be found here and I suggest you read it as it is very good information for anyone. It mentions the set screws used for corrector alignment. Once again everything depends on the user or what you are willing to settle for.

I actually made components for three Thermal Emission Spectrometers for three Mars missions and some of the tolerances on mating surfaces were a PIA and all this was to insure the least amount of mechanical alignment in the final assembly. My parts are still circling he planet on the Mars Global Surveyor some setting on the planet on two subsequent mission’s instruments, and yes I have bragging rights that is why I am blowing this horn. LOL LOL It is all that an old guy like me can hope for these days. I am not an optical engineer by an stretch just an old Tool & Die maker but like an old ship I have picked up a few barnacles along the way. I have a “fair” degree of understanding of the esoteric, and the emphasis is on the word “fair” only because of my many years in the trade and I might add that sometimes I am wrong. “To err is human.” Actually the only time I was wrong when I said I was wrong but was not! LOL LOL LOL

By the way as mentioned in the article it says “The instruments designer” actually not true! It is the matter of the “s”. I was “a instrument designer” not that instruments designer. Sometimes reporters make errors. I am sure that burned the butts of many at JPL. LOL LOL Unfortunately worlds may come and go but the Internet lives on forever. LOL

I have done a few corrector removals and reinstallations on Celestron scopes but not Edge scopes as I was shown how to do this by Dean down in Tucson. I know just enough to be dangerous. LOL The alignment by eye and is subjective at best especially by the great unwashed. With Dean he can do a good job because he has done thousands. On a regular Celestron and for eye piece viewing this may be acceptable depending on whether or not you are a purist. By the way for full disclosure I have a 14” Edge Celestron Scope. I bought mine before they were released and had to wait 4 months for them to be delivered.

Now on the Edge. This alignment of the corrector is done by set screws located around the periphery. This insures no shrinkage because shims are not used and a more precise location method was needed. With screws also comes inherent risks as you are screwing screws against the edge of the corrector. Now to be honest if you remove just enough set screws to free the corrector and leave in three you could theoretically remove the corrector do your work and then reinstall it pushing it to one side against the screws that you did not disturb but one would never know for sure that you had attained the alignment you had before that was done on an optical bench. And of course it goes without saying that the corrector has to be put back ?in at the exact same rotational alignment as it was before it was removed.

So you see the magnitude of the problem, there are caveats in any endeavor.

Depending upon your level of skill and “boldness”, read “cojones”, as Robert Frost would say, “Two Roads Diverged in a Yellow Wood, and sorry I could not travel both. And be one traveler, long I stood”. The choice is yours “Should I stay or should I go”? ?

Choose wisely but talk to Dean he is the master short of the factory and will give you the best advice. If you are within driving distance perhaps a road trip is in order besides I always learn when I go there even just to chat. You never know who you might meet there as Tucson is a hot spot for many astronomers.

You will not meet a finer man than Dean at Starizona, his crew, and of course his charming wife Donna and you can take that to the Bank.

Sorry I pontificated but you were warned and I never fail to abuse a captive audience! All this because of a washer! Yikes! LOL

Read the White Paper it is an interesting read.

Gary

Carpe Noctem