Welcome to


Web Site

Copyright P. J. Smith

EMail - re-construct address from the following line.

pjifl at bigpond dot com

But permission is given to distribute this material in unaltered form as long as it is not sold for profit.


Ronchi a comprehensive study.

Some Turned Down Edge Ronchi Patterns for an 8 inch F:6

Various Null Tests for Cassegrain Secondaries.

Simple 20c Shearing Interferometer

Simple Cheap Transverse Slide for Caustic Test



Function of an Eyepiece.

Eyerelief requirements and design problems.

Small, Long Eyerelief

Long relief, semi wide field.

8 mm, Long eyerelief of 18 mm, semi wide field.


5mm, narrow field, uses steel balls as laps

Planetary Eyepiece - Exquisite definition on a budget.

Large, Wide field, with very well corrected Exit Pupil Aberration

60 Deg, 60 mm, F:10 Simple

70 deg, 60 mm, F:6

80 deg, 70 mm, F:10

Huge Eyepieces

Huge Eyepiece Options - analysis and design

No Optical Glass required

Emergency eyepiece design uses NO optical glass

Distortion Characteristics

Examples of Distortion Curves from Typical Eyepieces


Small lens construction.

El Cheapo Diamond Tooling and Generating.

Micro Spherometer for Small Lenses


Large Photo Visual Cassegrain.

Sub Diameter Correctors for Cassegrains.

Sub Diameter Correctors for Newtonians



Taper turning setting gauge for extremely accurate setting of the lathe topslide.


A comprehensive study of the Ronchi Test and certain cassegrain null tests are covered. Some programs are available for download. See Software

Hopefully, small lens production for ATM'S and other amateurs will be supported. Eyepieces are a primary interest so eyepiece design and specifications will be featured. Some will use common optical glasses and other materials. Others will use more expensive optical glass types. All are from Schott. I often wonder why few amateurs ever progress to lens work. If it is due to the difficulty of obtaining optical glass then interested persons should look at page 3.

If there is sufficient interest I could be convinced to redesign for different glasses.

As an exercise, I suggest the construction of a Ramsden type of eyepiece from window glass. This will help test your technique for making small lenses and hopefully give you confidence. The performance of a Ramsden eyepiece with the short focus telescopes commonly found today will be found wanting but it can always be used as a magnifier to inspect ground glass surfaces and the like. .

Each of the eyepieces has very good or excellent definition extending nearly out to the edge. The focal planes do not have excessive curvature so are ideal for older viewers who have greatly reduced accommodation.

It is quite possible for an amateur to construct these eyepieces but workmanship, centring, and mounting of components must be well executed or performance will suffer.

The designs are not copied from any source but are the result of my own ray tracing.

Zemax design files for many of these eyepieces are available. These may be very useful for anyone who wants to dabble in eyepiece design as they can be correlated with the data on these pages. They have been placed on a web site dedicated to ATM software found at http://atmsite.udjat.nl/keyword.html, scrolling down to Software

I have no objections to anyone making these designs for personal use. Similarly, I have no objection to this material being copied for personal use but if any material is distributed to friends I DO EXPECT THE SOURCE TO BE CREDITED.

Addresses and links

The following is a list of links that may be useful. Small lens construction is not a mainstream issue for Amateur Telescope Makers (ATM'S) but the glass working techniques are common. Anyway, most homemade eyepieces are intended for amateur telescopes.

These links either provide information relevant to small lenses or are a good starting point to find other resources.

Amateur Telescope Making http://www.polaris.net/~tas/atm/atm.html

Mel Bartel's Home Page - ATM resources http://www.efn.org/~mbartels/

UK - ATM Resources http://www.aegis1.demon.co.uk/atm.htm

Newport Books on Lens making http://www.newportglass.com/book4.htm

Willman-Bell Inc. - books http://www.willbell.com/

Surplus lenses and optical gear - http://www.surplusshed.com


Mail address of author

EMail - re-construct address from the following line.

pjifl at bigpond dot com


Postal address of author