Cleaning a CDK17 mirror with Optical Wonder Fluid

In our Observatory installations, we have contact to customers for many years. This is why we get old telescopes for cleaning from time to time. This particular mirror is from a CDK 17" wich was used in a heavily poluted and salty area. The picture show´s that the mirror lost most of it´s reflectivity.

The fun fact about this is that after the cleaning our customer wondered why all his images where saturated. The reason was simply that the mirror got so much reflectivety back due to the cleaning, that the instrument was twice as fast as it was before.

The cleaning was done with Optical Wonder™ Cleaning Fluid.

To clean such a heavily poluted mirror, we lay it flat on the table and put a layer of one way tissues on the surface. This layer we make wet with Optical Wonder™ Cleaning Fluid and let it wet for some hours, so that all pollution softens up. Then we carefully remove the tissues and blow the pollution off the mirror with dry air. After this, we repeat the procedure again, but now we remove the tissues sideways from the mirror with no pressure. This step is repeated as often as necessary to get mirror free from particels which may scratch it.

Once all the heavy pollution is removed, we do a final cleaning run with Optical wonder and Optical Wonder Cloth to achieve a perfect finish of the surface.

Now, the mirror is good to go back to the tube and do some more years of observation.


Baader Optical Wonder, Celestron C14, Carl Zeis APQ 150Further examples: The cleaning in this example was done with Optical Wonder™ Cleaning Fluid.

The biggest advantage of Celestron SC and EdgeHD optics: Extreme longevity, because the optical surfaces remain protected for a lifetime. Even extreme dirt can be removed without residue within a short time.

To Celestron SC- and EdgeHD Optics (german webpage)


Wolfgang Paech

About the author

Wolfgang Paech has been practicing astronomy for more than 50 years. In addition to his many experiences with observatory domes of all kinds, his core areas are the Sun and the Moon. On the german Website you will find a complete moon atlas, recorded with his standard technique. But even in terms of Deep-Sky and Planetary imaging, as a veteran astrophotographer for many years, nobody can fool him.

The 50+ years of amateur astronomy with many other areas, such as the restoration of historical amateur telescopes, polar light trips and much more are prepared on his private german website at

View all posts from Dipl.-Ing. Wolfgang Paech
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