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Millennium Telescope Project. Aperture Fever…!. Objectives. Build large aperture portable telescope Maximise light gathering ability Lightweight open tube design Transportable to deep sky locations. Obsession 20” F/5 Completed scope. Babcock 24 inch. Design Goals. Ease of construction
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Objectives • Build large aperture portable telescope • Maximise light gathering ability • Lightweight open tube design • Transportable to deep sky locations
Design Goals • Ease of construction • Ease of assembly/disassembly • Ease of storage and transportation • Ease of collimation (repeatable)
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”)
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) Component Weights
22” F4.05 DesignSecondary cage and spider assembly with baffling
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
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Jaques Civetta, France465mm Dobsonian, fibreglass construction