Telescope mirrors

coated mirrorsAs a base material for making mirrors I use quality, fine annealed borosilicate glass with low thermal expansion and very low internal stress (≤20nm/cm). Standard glass for apertures up to 350mm is the Borofloat (made by Schott), 25mm thick, but I will also make you a mirror from thicker Supremax (also made by Schott) if you wish. 400mm and 450mm mirrors are made from Borofloat (25mm thick) or Supremax (35mm and thicker) and the biggest mirrors (500mm and 600mm) are made from Supremax (35mm or thicker) only. Grinding and figuring of optical surfaces run on special grinding machines under my permanent supervision. Because each and every mirror is custom made, I can pay maximum attention to the whole process. Repeated testing of the optical surface using Focault and Ronchi tests is a matter of course. Presently I am going to begin using Ross null test and very accurate test by interferometer. Stated quality of the mirror is guaranteed - it is a matter of my professional honour, that I will never let a substandard mirror to leave my workshop.

Below you can find prices of mirrors of common sizes and focal ratios I usually manufacture. In addition, I am able to make a mirror of virtually any non-standard size or focal ratio according to your needs. I try to do my best to meet customers requirements - be it parameters of the mirror, precision of the surface, unusual kind of coatings or professional interferometric test report. If you have any special wish, please contact me, I believe we will be able to find a suitable solution.

Mirrors of the Standard series have Strehl ratio better than 0.90, mirrors of the Premium series have Strehl better than 0.95. Test report is provided with every mirror. You can choose the type of coating - commonly used is standard aluminium with protective SiO2 overcoat with reflectivity around 90%. You can also decide for coatings with enhanced reflectivity (up to 96%) and better durability. Base prices includes standard Al+SiO2 coatings, additional charge for enhanced coatings is listed in the last column. Prices are in Czech crowns (1 EUR = 26 CZK, 1 USD = 18 CZK).

 

Parabolical mirrors price list

Aperture Focal length Price Enhanced reflectivity
Standard Premium
100 mm 400 mm 2190,- 2690,- 900,-
150 mm 600 mm 3890,- 4890,- 900,-
150 mm 750 mm 3190,- 3790,- 900,-
200 mm 600 mm 8790,- 10390,- 3900,-
200 mm 720 mm 7990,- 9490,- 3900,-
200 mm 850 mm 7290,- 8790,- 3900,-
200 mm 1000 mm 6790,- 7890,- 3900,-
200 mm 1200 mm 6390,- 7390,- 3900,-
250 mm 1000 mm 12390,- 14990,- 3900,-
250 mm 1250 mm 10490,- 12590,- 3900,-
250 mm 1500 mm 8490,- 11490,- 3900,-
300 mm 1200 mm 17990,- 20990,- 5000,-
300 mm 1350 mm 13990,- 16790,- 5000,-
300 mm 1500 mm 12490,- 15990,- 5000,-
300 mm 1650 mm 11990,- 14490,- 5000,-
300 mm 1800 mm 11490,- 13490,- 5000,-
350 mm 1500 mm 20490,- 24490,- 5000,-
350 mm 1650 mm 19490,- 23490,- 5000,-
350 mm 1750 mm 18490,- 22490,- 5000,-

Mirrors up to 350mm are made from 25mm thick Borofloat but I will also make you a mirror from thicker Supremax if you wish - don't hesitate to ask me for possible options.

 

Aperture Focal length Material Price Enhanced reflectivity
Standard Premium
400 mm 1600 mm BF 25mm 28990,- 32990,- 7000,-
400 mm 1600 mm SPX 35mm 36990,- 39990,- 7000,-
400 mm 1800 mm BF 25mm 25590,- 30990,- 7000,-
400 mm 1800 mm SPX 35mm 34590,- 37990,- 7000,-
450 mm 1650 mm BF 25mm 47990,-* 52990,-* on request
450 mm 1650 mm SPX 35mm 56990,-* 61990,-* on request
450 mm 1800 mm BF 25mm 42990,-* 47990,-* on request
450 mm 1800 mm SPX 35mm 51990,-* 56990,-* on request
500 mm 1800 mm SPX 35mm 60900,-* 77900,-* on request
500 mm 2000 mm SPX 35mm 58990,-* 65990,-* on request
500 mm 2250 mm SPX 35mm 57990,-* 63990,-* on request
500 mm 2500 mm SPX 35mm 54990,-* 61990,-* on request
600 mm 1800 mm SPX 35mm 180990,-* 195990,-* on request
600 mm 2400 mm SPX 35mm 123990,-* 132990,-* on request
600 mm 2700 mm SPX 35mm 135990,-* 144990,-* on request

* Standard material needn't be suitable for everyone in those apertures. If you opt for different glass (Pyrex), price may vary by great amount, so preliminary consultation is needed.

Professional, detailed interferometric test report is available for each mirror for 100 EUR. Tests and reports are done by prof. Wolfgang Rohr.

Delivery terms are based on agreement. Because each mirror is custom made, I require deposit covering the price of the material at the time of placing an order.

 

My offering of primary mirrors is completed by range of elliptical secondary mirrors. They are made from Borofloat, with surface accuracy better than λ/10. Price includes standard Al+SiO2 coatings, enhanced coatings are of course possible too.

Elliptical flats pricelist

Small axis Price
30 mm 600,-
35 mm 700,-
40 mm 800,-
45 mm 900,-
50 mm 1000,-
55 mm 1100,-
60 mm 1400,-
65 mm 1800,-
70 mm 2000,-
75 mm 2600,-
80 mm 3000,-
85 mm 3250,-
90 mm 4000,-
100 mm 4500,-

All mirror sizes will be delivered within 4 months.

 

About mirror testing

Focault testUntil now I tested my mirrors by simple classical Focault test in the center of curvature, using so called Couder masks.
Focault test is re-checked with Ronchi test performed using Ronchi grid. This method is sensitive to unwanted jumps between different zones on the surface of the mirror, turned edge, astigmatism etc.
Another new method I am using to improve accuracy of my measurements is Ross null test. It is so called "null test", where special lens is used together with Focault tester. This lens causes that mirror appears spherical in the tester and any zonal error is readily visible.
These tests are completed with star-test using artifical star. This method is very sensitive and allows me to evaluate rotational symetry of the mirror and reveal possible astigmatism.

Ronchi testResults of the measurements are processed by special software (Foucault test data reduce SW), that computes well known parameters P-V and SR. You can certainly object that this way of evaluating of the mirror is not accurate enough and derived P-V and SR values don't exactly have to match the reality. Therefore I sent several mirrors to be independently tested in the professional optical laboratory by prof. Wolfgang Rohr in Germany. It showed up that the differences among Strehl ratios measured by me and SR measured in the laboratory were lower than 2-3%. Based on my experiences and very thorough examining of each mirror I am pretty confident that for common mirrors (up to 500mm and f/4), my methods are accurate enough and stated parameters very well describe the real quality of the mirrors surface. Results of my measuremets are shown in the test report supplied with the mirror.

Most precise test method I am currently working at is an interferometric test done with the Bath inerferometer. It is probably the most sensitive method, used in all optical laboratiries and professional shops. Very accurately evaluates the shape of the mirror's surface and allows to exactly compute P-V, P-V RMS and Strehl ratios. I hope this test will be ready for use in next few months.