Northcote Hill Farmhouse

Northcote Hill Farmhouse, (off) Roseberry Rd, Norton,

Stockton-on-Tees. TS20 1LB. England.

Tel. 01642 554699 (Evenings please)

E-Mail: john_nichol@hotmail.com

Serving the needs of Telescope Makers

Interferometer

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

http://www.cloudynights.com/item.php?item_id=1865

May 2009: Need an Interferometer based analysis with your mirror? Click here.

November 2009: For clarification of mirror quality please click here

Welcome. Nichol Optical is a small business dedicated to making high precision astronomical optics. All of my products have a surface accuracy of at least 1/8 lambda P-V and a Strehl ratio of at least .86 unless otherwise stated. Telescope primary mirrors are made from low-expansion borosilicate glass usually a material made by Schott with a trade name of Suprax. I have been making astronomical optics for in excess of 30 years and have supplied optics to customers in Germany, France, Belgium, Denmark, Sweden 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, the double pass autocollimation test and interferometric testing. Parabolic mirrors are normally finished using the double pass autocollimation test, a test that is well regarded and widely used by professional opticians the world over. A certificate of quality is produced for each mirror manufactured. 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.

The picture to the left shows my laser interferometer, it is based around a high quality reference lens which can be seen at the front of the interferometer.

The picture to the right shows an interferogram of a 16 inch spherical mirror taken with the interferometer shown above. This mirror was made in order to test a 24 inch optical flat which I now use for testing parabolic mirrors using the double pass autocollimation test.

This picture shows my Ross null lens, this is a high quality interferometically verified plano-convex lens used for testing optics with aspheric surfaces including paraboloids, ellipsoids and hyperboloids.

The sequence of pictures above shows a 22 inch F4 mirror under the Foucault test.

The image shows the finished 22 inch diameter F4 paraboloidal mirror under the double pass autocollimation test using a Ronchi ruling. Straight bands indicate that the mirror is of high quality, in this case at least 1/8 lambda P-V.