The following pages detail the complete set of plans for an 18" Dobsonian based uponDave Kriege and Richard Berry’s excellent book.

Page 2 - Book p117 - Mirror Flotation System and Cell.Page 3 - Book p123 - Detail of Flotation System Triangles and Bars.Page 4 - Book p157 - Secondary Cage AssemblyPage 5 - Book p221 - Split-Blocks.Page 6 - Book p243 - Side View of Rocker Box, Ground Board and Side Bearings.Page 7 - Completed Telescope.

Page 1

Plans for building an 18inch f4.4 Dobsonian Telescope.More information can be found online, see url/qr code below.

http://www.ngc891.com/

18”(457mm)Mirror

Mirror Flotation System and Cell, p11718inch Mirror Tailgate is made of three mild-stell bars 25mm x 25mm (502mm long), and 2 mild-steel bars 6.5mm x 32mm (397mm long).Collimation holes are 10mm, tapped at 8mm - Split bolt hole size 10mm - Side pin hole size 10mm.Mounting hole sizes 8mm, 4 along each side rail, 2 along top rung.

Page 2

514mm502mm

251mm

397mm

194mm

141mm

13mm

41mm

6mm

25mm

25mm

25mm

6mm

Page 3

121mm

117m

m43

mm

148mm173mm

25m

m

Detail of Flotation System Triangles and Bars, p123Thickness of triangle 1/8" (3mm).Thickness of bars 3/16" (5mm).6 Triangles, 3 bars all in stainless steel.

Page 4

89mm

102mm

6mm

51m

m

41mm

36mm

46mm

22mm

521mm

479mm41mm 41mm16mm 279mm 16mm

562m

m52

1mm

479m

m41

mm

41m

m

Secondary Cage Assembly, p157Use low profile focusor on focus board. Also use extra wood to strengthen board see p168. Place focusor and board as close to tube as possible, allowing enough space for the full travel of the focusor.Use kydex on inside of tube. Tubes are 1" OD 0.871" ID 0.056" wall thickness (25mm OD 22.14mm ID 1.43mm wall thickness)MARK AND DRILL ALL HOLES BEFORE CUTTING RINGS! MAKE THIS AS LIGHT AS POSSIBLE, IT WILL REDUCE OVERALL WEIGHT AND EYEPIECE HEIGHT.

22mm

Page 5

89m

m

83mm

70mm 13mm

25mm

25mm

44mm38

mm

51m

m

Split-Blocks, p2218 required, 4 left-handed and 4 right-handed (i.e. mirror images of each other).

Page 6

25m

m 210mm410mm

420mm545mm

394m

m

320m

m

610mm

545mm76mm

15m

m15m

m

500m

m

76m

m32

mm

32m

m

127m

m

15mm 15mm

Side View of Rocker Box, Ground Board and Side Bearings.Height of rocker box (and therefore end board height) depend on balance and side of mirror box!Make feet and gap between rocker board and ground board as low as possible.Teflon pads should be between 65 and 70 degrees apart, depending on friction calculations, see chapter 9 p243 and section 10.3.

Page 7

25mm

210mm

410mm

420mm

545mm

394mm

320mm

610mm

1512mm

1512mm

1397mm 16mm

279mm

16mm

562m

m

521m

m

479m

m

41m

m

41m

m