Nichol Optical
Northcote Hill Farmhouse, (off) Roseberry Rd, Norton,
Stockton-on-Tees. TS20 1LB.  England.
Tel. 01642 554699
E-Mail:  or
Serving the needs of Telescope Makers
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Customer comment from Steve Jenner March 2014

Hi John,
The 20" f/4 mirror you refigured for me to sort out the problem it had of severe under correction is performing beautifully with lovely sharp star images. I have been able to use it at high magnifications with no problems at all. Your prompt professional service and friendly customer care made sure everything went smoothly and I got the mirror back very speedily. I found your prices very good indeed for the work carried out.
Observing the Virgo/coma cluster is simply amazing with galaxies showing real structure and details. The dipper bowl in Ursa Major had so many galaxies on show I think I need a better star atlas to identify them all, stunning.
Globular clusters are mind blowing at high mags with the star images tight and pinpoint. M3 at over 330x was incredible, filling the field of view with myriads of diamond like stars scattered on black velvet.
Your mirror in partnership with the Paracorr system is a recipe for a very happy deep sky observer indeed.
Thank you.

Customer comment from Laurent in France, 20 inch F4 mirror set (January 2013):

"I made the first light : The sky was not good but your mirror is very good  On Jupiter , with a collimation of 10 second with a laser , at 550x (without problem) we ( me and 3 friends ) saw no diffusion and no distortion of form  Good job !!! "


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Iris Nebula: image by Harry Page using optics made by Nichol Optical

Welcome. Nichol Optical is a business dedicated to making high precision astronomical optics.  I have been making astronomical optics for in excess of  30 years and have supplied optics to customers in Germany, France, Belgium, Denmark, Sweden, Netherlands, Ireland, Japan, Slovenia and South Africa as well as the UK.

To ensure my optics are of the highest quality a variety of tests are used. Together with the more traditional Foucault and Ronchi tests I also employ the Ross null test (using a certified lens), and the double pass null test or, autocollimation test as it is also known. These are well established tests and are used widely by professional optical shops the world over. Parabolic mirrors are generally finished using the Ross null test or autocollimation test, these tests are quantitative in nature and do not produce a set of numbers describing the mirrors surface. I do not produce a test certificate giving a detailed numerical analysis of  a mirrors surface.  With a null test a perfect mirror produces straight bands when viewed with a ronchi grating, any curvature of the bands indicates the amount of spherical aberration present. For a given mirror a computer simulation may be generated showing the degree of curvature in the observed ronchi bands for varying degrees of spherical aberration. In order to assess a mirrors surface the observed curvature of the ronchi bands is compared with a computer generated image. With experience this test method is easily capable of revealing wavefront errors of  1/8 wave and smaller. For more information about optical standards please read the notes on my articles page. Perhaps the best recommendation for any optic is confirmation of it’s performance in a telescope, I am pleased to say that I have received much feedback from customers who have been delighted with the performance of their optics, for further information please see the comments page.


The image shows a 18 inch diameter F4.3 paraboloidal mirror under the double pass autocollimation test using a Ronchi grating. Straight bands indicate that the mirror is of high quality, in this case at least 1/8 lambda P-V surface error.

For an independent assessment of one of my mirrors please see this link

For clarification of mirror quality please click here

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