Lenses

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.

 

127mm diameter f/12 R30 objective lens by I R Poyser

127mm diameter f/12 R30 objective lens

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: £600.00 plus delivery

82.55 mm diameter objective lens

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

102 mm diameter objective lens

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.

Lenses for eyepieces, relay lenses and objective lenses

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

 

More lenses – ‘oddments stock’

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.