Introduction: Making 22 Inches Dobsonian Telescope Body Under 100$
- 1 inch steel plate 4mm thick,
- 1 inch aluminium square pipes for strutts,square steel pipe 5 mm for body,
- teflon pads,
- wooden blocks,
- basic welding and carpentery instuments,
Step 1: MAKING OF ALTITUDE BEARING.
MATERIALS REQUIRED FOR ALTITUDE BEARING
Can use altitude bearing- more than diameter of the glass preferably 1.5 to 1.8 times .
Make 32 inches semi-circle with 1inch thick steel plate. Give support to the bearing in three equal side of circle. Make two altitude bearing. please see image
Step 2: BASE FOR PRIMARY MIRROR
Base square with steel pipes of 25inches.
- Divide it into 4 parts by dividing it into 2/3 & 1/3 respectively (refer diagram)
- now, weld a sphere made out of door handle at the centre of square for support of primary mirror cell.
- mirror cell should have a similar size cup for balancing of mirror.
- drill four corresponding 1/4 holes in base plate and mirror cell.
- cut head of 1/4 nuts of 3 inch and weld at edge of square.
Step 3: MAKING OF UPPER OPTICAL ASSEMBLY
- Take two rings of 24inch in diameter(1 inch width) and joint them in parallel by giving support of 3 aluminium bar (1 feet x 1 cm).
- secondary holder attachment to be done on upper ring.
- 6 inch plate is weld at centre of upper ring by using 3 aluminium bar placed at equal distances.
- secondary mirror holder : Drill 4 holes in plate(one at center & 3 in equilateral sides).
Step 4: STRUTTS
- Take 1 inch square aluminium pipe and insert wooden plate inside for stability.
- Height is calculated according to the focal length of mirror.
- Drill ¼ size holes at edge of the pipe for connecting upper and lower optical assembly
- Weld 2.5 inches steel rod at edges of upper and lower optical assembly for strutts attachment.
Step 5: PRIMARY MIRROR CELL.
- base wooden 25 inches circle in diameter is used
- in the center of wooden plywood attach a metal cup of the size of the sphere which is on the base square with support and secure properly with metal plates so that weight is distributed properly
- drill four holes in the base square corresponding to the base plate of mirror cell
- place 5 inch 1/4th nut at the corresponding holes made on the woooden base. this helps in collumianting the primary mirror by putting springs in the nut. weight of my mirror is 30kgs & difficult to colluminate such mirrors.
- central balancing of mirror helps & gives less pressure on spring making it easy for the mirror to be tilt & colluminated.
Step 6: ROCKER BOX
place 2 wooden blocks apart at a distance of 25mm+4mm ( 4mm for the easy movement of the altitude bearing(in my case) 9 inches
make a notch on the wooden block of the size of altitude bearing.
place teflon pads on all four wooden blocks
take a similar size base plate for rotation movement of azimuth
put a teflon on centre. as my assembly is heavy i required more teflon pads
nylon pads were drilled at the base
Participated in the
Space Contest 2016
6 years ago
6 years ago
where do you get the primary mirror?
Reply 6 years ago
Thanks for your inquiry. Glass blank has been made by fusing three plate glass of 19mm in furnace. it work well with no optical issues. could make 4 such blanks of 2 no of 16 and 2 no of 22 inches.