Millennium TelescopeProject

Aperture Fever…!

Objectives

• Build large aperture portable telescope

• Maximise light gathering ability

• Lightweight open tube design

• Transportable to deep sky locations

Obsession 20” F/5Completed scope

Babcock 24 inch

Design Goals

• Ease of construction

• Ease of assembly/disassembly

• Ease of storage and transportation

• Ease of collimation (repeatable)

MMT Activities...

Mirrors

Primary Mirror (Pyrex):– Diameter, 482 mm (19”)

– Edge thickness, 38 mm (1.5”)

– Focal length, 2165 mm (F/4.5)

– Calculated weight 15.6 kg (34 lb)

Secondary Mirror (elliptical plate glass):– Major axis, 150 mm (5.9”)

– Minor axis, 106 mm (4.2”)

– Thickness, 14.5 mm (0.6”)

Component Weights

Primary Mirror 15.39 kg (33.9lb)

Mirror cell base 5.48 kg (12.1lb)

Wiffletree 1.79 kg (3.9lb)

Rocker bearing (x2) 3.62kg (8.0lb)

Al bearing runner (x2) 0.80 kg (1.8lb) (optional)

Strut blocks (x8) 0.78kg (1.7lb)

Cross bars (x2) 1.38kg (3.0lb)

Base total = 28.43 kg (62.7lb)

(excluding Al runners)

8 x Struts (total) 4.11kg (9.1lb)

Cage ring 1.10 kg (2.4lb)

Secondary mirror 0.4 kg (0.9lb)

Focuser (est) 0.24kg (0.5lb)

Spider (est) 1.30kg (2.9lb)

Viewfinder (est) 0.45kg (1.0lb)

Telescope total 36.5kg (80.5lb)

Mirror Cell

Obsession 20” F/5Mirror cell assembly

Babcock 24” F/4

22” F4.05 DesignSecondary cage and spider assembly with

baffling

Obsession 20” F/5Truss tube clamps

Obsession 20” F/5Inserting mirror

16” F/3.75 String Telescope

Base

22” F4.05 DesignCutaway of bottom frame and drives

16” F/3.75 String Telescope

In car!

Extras - Other Designs

• Internet a great source of information providing inspiration!

• Ultra-light designs evolving from more traditional Obsession

• MMT uses best features of all these designs

Sayre 22 inchCAD drawings

Dan Gray 16” F/3.75 Completed scope

16” F/3.75 String Telescope

Disassembled scope (fits in a hatchback!)

Gary Wolanski, USA16” F/5 Dobsonian, 40 Pound, all-metal construction

Jaques Civetta, France465mm Dobsonian, fibreglass construction

Doug Tanaka, USA12.5” F/6 String-Truss Dobsonian