If you are building your own telescope its quality will be decided by the quality of the OBJECTIVE lens – the large lens at the front of the telescope – and the EYEPIECE lenses.
In this section we describe the lenses that we can offer, all of which are of high quality and suitable for telescope-making.
These lenses were designed and made at our request by ISTAR Optical, of Arizona, because we had not found it possible to obtain sufficiently good objective lenses on the open market.
These superb lenses are intended for use in our range of large brass refractors, but we are also going to offer some for sale to those amateur telescope makers who have reached the stage of building their own large refractor.
Design: ISTAR Optical call this prescription their ‘R30 Anastigmat’. The lens is an air-spaced achromatic doublet. Istar claim that its optical performance is equivalent to an apochromat.
Finish:All four surfaces are multi-coated
Diameter:Clear aperture is 127 mm (5 inches)
Focal length: 1500 mm
Cell: Each lens is supplied in an alloy cell, black anodized. The cell is of the ‘push-pull’ design to aid squaring-on when the lens is fitted to the optical tube assembly.
| Outside diameter of cell flange: | 168 mm |
| Holes in cell flange: | pairs of M5 threaded and 5 mm plain hole |
| Pitch circle diameter of holes in flange: | 158 mm |
Performance:The optical performance is superior to the conventional achromatic doublet, due to the choice of glasses and design of the curves.
Each lens is hand finished and is individually star-tested before it is shipped to us.
Availability: These lenses are made for us by ISTAR. Only we hold them in stock.
Price: £822.00 plus delivery
These lenses are British-made cemented doublets. They are intended for those who wish to make their first serious astronomical refractor. They give good optical performance in a telescope that is easily portable. The metal tube necessary to mount these lenses is readily available from metal suppliers.
| Diameter: | 82.55 mm (3¼”) |
| Focal length: | 1000 mm |
| Description: | Cemented doublet. Not anti-reflection coated. |
Price: £160.00
We have ONLY ONE of these lenses. It was made especially for us by Jim Hysom – the famous lens-maker who ran the firm of AE Optics at Cambridge, England.
Jim made a lot of these lenses for us when we used to market our range of Rochester 4-inch refractors. This is the very last of those lenses; its optical performance is excellent.
| Diameter: | 102 mm (4” inches) |
| Focal length: | 1520 mm |
| Description: | Cemented doublet. Not anti-reflection coated. |
Price: £640.00 – only one available.
This list shows some of the lenses that we hold in stock. Those lenses whose catalogue number begins with 5 are brand new and unused. Those lenses whose catalogue number begins with 9 are mounted in a metal cell.
|
Number |
Diameter (mm) |
Focal length mm (ins.) |
Price £ |
Comments |
| 1000 | 9 | 20 (0.8) | 15.00 | These can be used in identical pairs to make eyepieces. The focal length of the eyepiece will be about HALF the focal length of the individual lens. |
| 5108 | 12 | 30 (1.2) | 15.00 | |
| 1118 | 14 | 38 (1.5) | 15.00 | |
| 5010 | 9.5 | 15 (0.60) | 15.00 |
These beautiful achromatic doublets are brand new and are anti-reflection coated. They can be used for making eyepieces. |
| 5020 | 9.5 | 18 (0.71) | 15.00 | |
| 5030 | 11 | 28 (1.1) | 15.00 | |
| 5040 | 14.2 | 56 (2.2) | 15.00 | |
| 5050 | 17.5 | 61 (2.4) | 15.00 | |
| 5060 | 14.5 | 89 (3.5) | 15.00 | |
| 1114 | 17.8 | 48 (1.9) | 20.00 | The preferred choice for RELAY LENSES |
| 5281 | 21.5 | 53 (2.1) | 17.00 | |
| 5293 | 25.2 | 56 (2.2) | 20.00 | Used in our own 35mm Plossl eyepieces. Highly recommended. |
| 1283 | 19 | 61 (2.4) | 15.00 | |
| 1401 | 39.6 | 99 (3.9) | 13.50 | Some marks, but make superb eyepieces |
| 1391 | 25 | 102 (4) | 15.00 | Plano-convex. Ideal for eyepieces or relay systems.
1392 is anti-reflection coated |
| 1392 | 25 | 102 (4) | 16.00 | |
| 1393 | 25 | 102 (4) | 16.00 | Bi-convex. Excellent for eyepieces or relay lens systems |
| 5398 | 26 | 102 (4) | 15.00 | |
| 9390 | 26 | 102(4) | 15.00 | Threaded and flanged brass cell |
| 5392 | 29 | 102 (4) | 15.00 | |
| 5400 | 26.7 | 104 (4.1) | 20.00 | Not cemented. Beautiful |
| 1404 | 28 | 104 (4.1) | 15.00 | |
| 5424 | 31.2 | 109 (4.3) | 20.00 | Beautiful |
| 1405 | 48.5 | 109 (4.3) | 18.00 | All have edge chips but excellent for making HUGE eyepieces. |
| 5407 | 24 | 119 (4.7) | 20.00 | Beautiful |
| 9400 | 30 | 122 (4.8) | 10.00 |
Brass cells. Slight barium stains. Lovely for small finders. |
| 1411 | 39.6 | 107 (4.2) | 16.00 | Slight marks but excellent for eyepieces |
| 5422 | 25.9 | 124 (4.9) | 20.00 | Beautiful |
| 5434 | 31 | 127 (5) | 20.00 | Beautiful |
| 5436 | 29.5 | 127 (5) | 20.00 | Anti-reflection coated on rear surface |
| 5466 | 31.2 | 127 (5) | 18.00 | Not cemented, coated, beautiful |
| 5467 | 31.2 | 127 (5) | 20.00 | Beautiful |
| 1461 | 31 | 135 (5.3) | 15.00 | |
| 2411 | 39.5 | 117 (4.6) | 15.00 | |
| 2413 | 39.5 | 117 (4.6) | 18.00 | Same as 2411 but anti-reflection coated |
| 1464 | 31 | 140 (5.5) | 20.00 | Reverse configuration, front element is flint. Superb. |
| 1465 | 31 | 140 (5.5) | 20.00 | Standard configuration, otherwise as 1464. Superb. |
| 1470 | 31.5 | 147 (5.8) | 15.00 | |
| 1472 | 36 | 147 (5.8) | 15.00 | |
| 1476 | 31.5 | 155 (6.1) | 15.00 | |
| 5500 | 25 | 1655 (6.5) | 20.00 | Beautiful |
| 5522 | 28.5 | 168 (6.6) | 20.00 | Beautiful. Anti-reflection coated |
| 9530 | 50 | 178 (7.0) | 20.00 | Brand new, in cell. Ideal for 7 X 50 finders. |
| 5900 | 52 | 330 (13) | 22.00 | Brand new, coated. Ideal for 10 X 50 finders. |
| 10 | 31.5 | -51 (-2) | 7.00 | Not achromatic. Biconcave |
| 15 | 18 | 43 (1.7) | 7.00 | Not achromatic. Planoconvex. For eyepieces |
We have a large quantity of achromatic doublets in stock, of which we only have a few of each diameter and focal length.
If you need just one lens for a particular project and you do not see what you require on our website you may wish to get in touch with us to discover whether we can supply it from our ‘oddments’ stock.