A low-cost Small Refracting Telescope G++
The telescope that is described here was first developed at Inter-University Centre for Astronomy and Astrophysics, Pune in 2009, during the International Year of Astronomy. We called it G++ ( Galileo plus plus) as it was an achromatic lens and Ramsdon eyepiece.
Using this telescope you can observe the Moon, occultations of bright stars, the moon of Jupiter, phases of Venus and just about make out that the Saturn has rings.
And you can project the Sun for various solar observations.
Most of the parts for this telescope are available in the market and has some custom made items. and some off the shelf picked up plastic tube material used mostly by irrigation industries.
Bill of material:
| Item no. | Item | Dimension | Quantity |
| 1 | Achromatic lens | diameter 45 mm / focal length 45 cm |
one |
| 2 | Lens holder | one | |
| 3 | 45 degree mirror | one | |
| 4 | Eyepiece | focal length 25 mm | one |
| 5 | PVC tube for the telescope | 50mm outer diameter / 35 cm long |
one |
| 6 | Reducer | 50 to 40 mm | one |
| 7 | Cradle or service saddle | for PVC tube (item no 1) | one |
| 8 | Threaded coupler | 32 mm | two |
| 9 | Elbow (threaded) | to fit threaded coupler (item 4) | one |
| 10 | Elbow to cradle coupler | one | |
| 11 | End flange | for reducers (not essential) | one |
| 12 | Stand pipe | 32mm outer diameter / 35 cm long | one |
| 13 | Wooden board (we have used Chakla used for making roties) | 25 cm x 25 cm (thickness about 2 cm) |
one |
The assembly of the telescope is very simple and can be easily carried out from the pictures given below.
The parts 1 to 4 were purchased from Tejraj and Co in Mumbai, India and rest from local suppliers of irrigation material.
Point to be noted here is that that the end flange is not absolutely essential. One can always drill hole in the wooden plank and fix threaded coupler into it. What is important is the PVC tube for the telescope. It’s outer diameter should 50 mm and the reducer should be 50-40 mm so that 45 degree mirror assembly can go into it. The cradle should clamp the telescope tube.
For rest of the mount one can be flexible.
DIYA 