I am pleased to offer as well retouching and resurfacing of your mirrors in use. Pricing depends on:
- Type and magnitude of surface defects. These can be diverse, so an appropriate effort estimate can be given only after an measurement in my optical shop.
- Type of coating. A highly reflective mirror layer (more than 92% reflectivity) must be removed under certain circumstances much more effortful than an ordinary 88% aluminum layer. If you do not know which mirror coating is deposited, I'll name two prices for both scenarios.
- Condition of polish. If a mirror is not completely polished-out, you will have to decide whether this deficiency should also be eliminated. This may mean a few hours of extra polish. In extreme cases, however, the final grinding must be completely carried out again, which means a lot of extra effort.
- Please contact me including information on the diameter, focal ratio, origin of the coating (if known), mirror thickness, substrate (if known). Please also mention your observations as to why you think the mirror is probably deficient. I will then call a first, yet non-binding cost estimate for retouching.
- If you think my cost estimate is appropriate, there are two ways of proceeding: You can send your mirror to the company Wellenform, who is most trustworthy in optical metrology in Germany. They will accurately measure and document the status of your mirror and will dispatch it to me afterwards.
Or you can send your mirror to me, and I will personally measure your optics.
In both cases, a report will be created, including interferometric analysis. Once I know the result, I can confirm the initial cost estimate or will correct it, if the defects are larger (or smaller) than expected.
- Following this you can decide how to proceed further. If you are satisfied with the result of the evaluation, and you think, no work needs to be done, I will send the mirror back to you. I will charge you only the interferometric evaluation done, as will Wellenform do. My price for measuring is usually around 100 Euro; for large and thin mirrors I charge up to 150 Euro. For Wellenform’s prices please take a look at their price list on www.wellenform.biz.
If you are not happy with the result of the evaluation of your optics and want to get a retouch, I would start as soon as possible after your expressed decision.
The time for completion is determined by order position, type and size of defects, and set in accordance with the delivery times of the coating company to which I send the mirror to be aluminized. Be sure that I will send you the final result of the evaluation of the retouch for achieving your acceptance and I will only send your mirror to the coating company after acceptance of the retouching process.
Before I start working, you will get a rough estimate of the time to completion. Please note that the exact date is hard to predict and depends on many factors. Always true: In precision optics you cannot rush, because quality overrides speed! You should be absolutely satisfied with the result - this is my priority.
An example of a successful retouching
The graph shows a 300mm f/5 mirror in condition as delivered. The massive astigmatism degrades the Strehl to unacceptable levels.
As you can see on the conic constant in the picture, I will leave all mirrors slightly under corrected. This is done deliberately, as each mirror tends to overcorrection during his permanent lagging behind the decreasing temperature overnight.
Please note before making a request:
If your optics shows massive damage, it would be helpful if you could please send photos of the damage in advance.
Small optics of BK7 or float glass (they often have slightly greenish shimmer) are barely worth a retouching. The costs of my effort and of the resurfacing will pretty sure exceed the purchase price of your optics. I therefore usually reject a revision, not at least because of mirror substrates with considerable internal stresses, where a permanent shape is almost impossible.
I am sorry to also refuse optics with center bore (Cassegrain, Ritchey-Chrétien, etc.), as their subsequent optimization is currently beyond my capabilities.