corrector plate re-coating

[jordan20]

dose anyone out there who can re-coat corrector plates as at sometime in the future i would like to have my mk66 done even though the views are very good.

[johninderby]

Orion Optics UK re-coats correctors and they do have some very good coatings.

John

[AndyH]

Mmm.

Orion Optics make Maks, so I'd guess they could do it, BUT at a price, especially as it's not an O.O. product.

The corrector doesn't look too bad in your pics? Or is it worse than it looks??

Andy.

[jordan20]

its a little worse than it looks but if you look straight on the tube from 5 feet you can see it but if you get close and look from the side you can see the damage.

[jordan20]

i emails orion optics yesterday and this is what they told me

Hi,

"We are unable to remove and re-coat corrector's, sorry. You have to polish the old coating off and without knowing the exact radius of the surfaces it is not possible to do.

Regards

John"

i have been told they can re-coat correctors of any kind upto a size. so this dose not add up.

[John]

I think what they are saying is that the process of removing the old coating could impact the figure of the corrector and, as they did not manufacture the scope and therefore don't have the precise specifications, they don't want to take responsibility for that.

This does seem a little strange because, as far as I know, they do handle the removal of coatings and re-coating of mirrors that were not manufactured by them

I could be because the relationship between the corrector and the primary in the mak-cassegrain has to be exactly matched I guess wheras they know the radius of curvature for a mirror of a given focal ratio.

[johninderby]

I do remember someone saying they had an SCT re-done by OO a few years ago. Maybe now they just don't want to get involved in something that could go wrong.

John

[michael.h.f.wilkinson]

Recoating a mirror for a Newtonian is a very different proposition from recoating a corrector, as suggested above. Corrector and primary are matched, whereas the correct figure of a Newtonian primary is just a parabola, and an ever so slight change in focal length of the primary is unimportant. Secondaries need to be flat, so no guesswork involved. I assume they do recoat their own brand corrector plates, and perhaps for those brands that are willing to supply the optical details.

[michael.h.f.wilkinson]

I had gathered many modern primaries also combine aluminium with one or more dielectric coatings. I had assumed these would also need removal by polishing, but maybe an acidic solved can penetrate the dielectric sufficiently to attack the underlying aluminum.

[AndyH]

I could be on the wrong track here, but doesn't the Rumak style MK-66, have a removable secondary mirror ? Or, are these coatings you're talking about, on the miniscus itself?

Andy.

[jordan20]

the secondary can be removed and i have found someone else who will do it for £100 including realignment of the optics

OO that £600 price tag made me and him laugh !

[JohnGlenn]

Sorry to refloat a so old message but I have a very similar problem. I have an Intes MK67 with a corrector plate with many small scratches. It is quite sad to have a scope like this in this state. Does anyone know any place in Europe that could fix a problem like that?

[Peter Drew]

Hello John, welcome to this forum. It's most unlikely that the scratches you mention will have any significant affect on your telescopes performance. As you say, it's sad to see optics in other than pristine condition but as it is probably just of cosmetic importance it's difficult to justify the high expense needed to rectify it. As mentioned early on in the thread, coatings can be removed only by polishing which inevitably alters the figure, the process most likely mean that the internal coating would also be spoiled and need the same treatment. Maksutovs lend themselves to mass production but for a company to undertake a one-off would not be worthwhile unless a high charge was made. I speak as a retired telescope maker who used to specialise in Maksutovs.