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Antique and Historic Telescope Objective Lens Replacement, Repair and Restoration


1885 Grubb 8" Refractor Objective, Yale University
Cleaning and re-assembly

I design and make replacement objectives for antique and historic refracting and reflecting telescopes that have either had their objectives damaged or lost. Over the years I have worked on and studied historic telescope optics. The subject of working on antique telescope optics is a sensitive and controversial one. For one thing, as regards refractors, it is never really possible to re-create an old, lost objective; glasses have changed (for the better) and designing defects into an objective in order to make it 'historical' never really works. The other controversy is whether or not old existing objectives should be worked on. In my opinion, re-working existing objectives for any reason can result in the damage and even the loss of an irreplaceable historic artifact, not to mention serious reduction in antique or historic value. Polishing a surface creates a new surface with a different polish, the original optician's work is lost. In the case of a missing objective, my basic approach is to make a new objective to the highest modern standards and out of modern basic glasses that would be considered 'achromatic'. For example, I would replace a lost 1870 period 6" f/15 telescope objective with a modern air-spaced equivalent using BK7 and F2 glasses and no AR coating. Other glasses can be specified upon request and details of correction discussed but you see the general philosophy.

Services are detailed as follows:

1. I design and manufacture new replacement objectives for any type of both refracting and reflecting telescopes, simple and compound. We can enter into discussions about the type of color correction and choices of glass to best suit your historic instrument and bring it back to a fully functioning condition.

2. I will not re-touch existing optics except in the most extreme cases where the surfaces have been rendered unusable. This includes the removal of AR and other modern coatings that have been applied to period or historic optics. Any attempt to remove these coatings mechanically (polishing) will alter the polished surface, alter and possibly destroy performance, and reduce historic monetary value. Many of these historic lenses have aspherized surfaces and polishing will alter the aspherization and result in a non-functioning objective. There is no such thing as 'just polishing off the coating'. If someone tells you this, they do not know what they are talking about.

3. Objectives that are incomplete (missing element) are best completely made over with modern glasses. Unless the specifics of the remaining glass are precisely known attempting to design a new replacement element will likely result in poor performance.

ca.1920s-30s Mogey 6.5" Refractor Objective
Cleaning and re-assembly