Handcrafted Custom Telescopes and Precision Optics

Independent Control Tests by Wolfgang Rohr

We present to you, the results of two tests on two of our mirrors. These were done by an independent expert.

The first mirror is part of an AR 300UL Gemini telescope that a customer ordered. The diameter of the mirror is 300 mm with a thickness of 25 mm and a focal ratio f / 4.6 . The mirror was sent for coating to Orion Optics with 98% reflectivity and sent from there to Mr. Rohr for testing.

It was important for us to obtain affirmation of our product’s quality from an independent source so that our customers can be sure we are offering them something of high standard. The independent expert that we chose to test the mirrors is well-known in the field of amateur astronomy, the German expert Wolfgang Rohr. The results of his tests completely confirmed the validity of our results and the excellent quality of both mirrors.The results of the first mirror are as follows: Strehl = 0.987, lack of astigmatism, smoothness of the surface and lack of zoning.


"Dear Mr. Stoykov,
I was ordered from Teleskop Service to test your fine Newton mirror. Now the test results:

First I checked at Radius of Curvature for any rest astigmatism of the mirror itself, not from the setup. This fotos shows a very small amount, so there is
no significant astigmatismus of that mirror.

Astigmatism test, Wolfgang Rohr


In a second step I use a autocollimations setup mit a 400 mm flat.  See here: http://rohr.aiax.de/autokollimat.jpg

Interferometry test, Wolfgang Rohr


These are qualitative tests, that shows, how smooth the mirror surface is - you will enjoy this. The Foucault test without zones, the Ronchi test

with straight lines and at last the Lyot or roughness test that shows a very fine surface. Here is a report with different roughness of mirrors.

Foucault, Ronchi, Llyot test, Wolfgang Rohr


Many regards

Wolfgang Rohr,  http://r2.astro-foren.com/index.php/de/


The second mirror is part of an order of five mirrors for Telescope Express, Germany. The mirror has a diameter of 400 mm, a thickness of 25 mm and a focal ratio f / 4.5

The results also indicate excellent quality: Strehl coefficient = 0.993, lack of substantial astigmatism, smoothness of the surface and lack of zoning. Photos from the second test can be seen below.