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This document outlines the crucial design requirements and goals for a portable telescope intended for easy transportation and assembly. Key highlights include a portable design suitable for non-dome use, a lightweight structure for easy handling, and a flexible mirror cell that maintains optical integrity. The specifications established focus on minimizing component weight and optimizing design for rapid assembly, while ensuring mechanical rigidity. Potential upgrades for automatic tracking and considerations for manufacturing materials and techniques are also discussed.
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Millennium Telescope Meeting 2 Requirements and Design Goals
Portability • The telescope unlikely to be used in dome or on balcony- so must be portable. This also implies it must be de-mountable and easily assembled.
Mirror • The mirror spec is fixed; the cell must be designed to support the 'thin' 19" mirror without significantly degrading optical performance.
Height • Primarily fixed by mirror focal length and diameter- otherwise the lower the better, minimises the climb up a ladder. Will be approx 7 feet.
Footprint • The disassembled telescope should fit into a hatchback- e.g. Golf or Focus. • Must be easily stored at OASI e.g. in storage area at bottom of dome steps.
Weight • All de-mounted components should be capable of unaided lifting and manoeuvring by two (unexceptional) persons; imposes an upper limit of about 60 pounds per component.
Open Structure • Avoids fans and promotes rapid cooling of the primary. Less prone to wind vibration. Minimises weight.
Struts/Truss-Tubes • Short enough to fit into a hatchback; look into multi-section struts; struts cannot exceed a certain length (subject to design). • Can we use 6 struts rather than 8; this simplifies telescope balance and reduces weight?
Stiffness • Minimise flexure with rigid structures.
Rocker/Mirror Box • Rocker may be more elegant, simpler to make and achieve weight targets - but design is more speculative. • Mirror box is proven design but much heavier- and may not meet design requirements.
Secondary Cage • Keep as light as possible- consistent with mechanical rigidity. • Design should consider (optically) best available eyepieces- probably 2". • Secondary mirror pre-alignment should be designed-in. • Design needs to be safe for transportation.
Optical System • Mechanical assembly must be repeatable such that telescope is approximately pre-aligned. • Telescope must be capable of easy remote-site fine-alignment.
Baffling • Upper cage and primary mirror baffles need to be de-mountable and easily installed.
Drive System • Although initially envisioned to be manually tracking, it would be highly desirable to be capable of upgrading to automatic tracking, at a later date.
Economy of Materials • Minimise costs by keeping material weight down. • Use plywood + steel where possible and standard components if available.
Economy of Machining • Design as many non-standard components as possible that can be produced "in-house". Consider use of plywood, for rocker or mirror box, etc; and Martin's metal working expertise for other components.
Gary Wolanski, USA16” F/5 Dobsonian, 40 Pound, all-metal construction
Gary Wolanski, USA16” F/5 Dobsonian, 40 Pound, all-metal construction
Gary Wolanski, USA16” F/5 Dobsonian, 40 Pound, all-metal construction
Charlie Wicks, USA20” F/4.5 Dobsonian - all-metal construction
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