It took a long time to improve the production of my optics to offer a broad range of different mirrors now. My main interest is on parabolic primary mirrors for Newtonian telescopes. I also work on flats, spherical, ellipsoid mirrors (e.g. for Dall-Kirkham-telescopes), or hyperbolic optics (e.g. for Ritchey-Chrétien-telescopes). Since the latter could only be realized in close coordination with the customer, please contact me to express your expectations and the purpose of the mirror.
Please find a table with my usual and standard sizes of common primary mirrors for Newtonian telescopes below. In addition to my standard sizes I can realize any other size from 12’’ to 32’’, any focal ratio from f/2.7 to f/∞, any substrate thickness from 21 to 47 mm. As focal lengths of more than 3200 mm require a larger effort, please ask explicitly for conditions.
Usually I use Schott Borofloat 33 or a substrate with equal physical properties. Borofloat 33 is established as best substrate for the sizes listed above. Any other kind of glass should be provided by the client.
If you would like to use glass ceramics instead of borosilicate glass because of its low thermal expansion coefficient, please bear in mind: Small and medium size mirrors are not limited by deformation of the surface under changing temperature, but by turbulence immediately in front of the mirror’s surface. This turbulence is fanned by the great thermal mass of the primary mirror and is maintained by the falling temperature during the night. Actually Zerodur has this turbulence in the same degree as any other glass of this dimension. What initially sounds advantageous – no thermal expansion of Zerodur – is done to naught in practice by the far more harmful releasing heat in form of turbulences because of the primary mirror as heat reservoir. As top priority, a mirror as thin as possible should be chosen. Only then you should think about employing a better substrate quality than borosilicate glass provides.
Please note: Details of focal lengths and focal ratios are approximate figures! Usually my optics have a scattering in the focal length of up to +-3%. A mirror having a desired focal length of 2000mm actually receives a focal length between 1940mm and 2060mm. Of course a lower tolerance (down to +-1%) is possible, but this must necessarily be settled in advance. The average surcharge on the prices listed below for smaller focal length tolerances will be between 5% and 15%.
Which quality can be expected?
The table above gives an overview of the minimum Strehl value guaranteed by me, depending on the diameter and the aperture ratio. Basically, this is the minimum accuracy which is usually significantly exceeded. In this context please note my Examples-page and here I describe the measurement method in more detail.
If you have specific requirements, please do not hesitate to contact me.
You are looking for the greatest possible transparency when buying your telescope optics?
I enclose a CD to every mirror I deliver, containing the complete interferometric final evaluation. This CD contains every used interferogram of all measurement positions, and all software evaluations. You can also find a Quick Start Guide, which allows you to self-evaluate the interferograms.
A serial number is engraved on the back side of every mirror. This serial number can be found as watermark on all enclosed interferometric single shots, so an unambiguous assignment of evaluation and the optics delivered is guaranteed.
Standard price list for Newton-parabolic mirrors of Schott Borofloat or Supremax
For general information about ordering, purchase, and delivery please check my Terms & Conditions.