Download Millennium Telescope

Millennium Telescope
Meeting 2
Requirements and Design Goals
Requirements...
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 prealigned.
 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.
FAS Website Trawl...
John Cross, Bristol AS
14” F/4.5 Dobsonian
Jim Brace, Wadhurst AS
18” F/5 Dobsonian
Gary Poyner, Heart of Eng AS
18” F/4.4 Dobsonian
Wadhurst AS, Norfolk
Other Designs…
Alternative materials
Gary Wolanski, USA
16” F/5 Dobsonian, 40 Pound, all-metal construction
Gary Wolanski, USA
16” F/5 Dobsonian, 40 Pound, all-metal construction
Gary Wolanski, USA
16” F/5 Dobsonian, 40 Pound, all-metal construction
Charlie Wicks, USA
20” F/4.5 Dobsonian - all-metal construction
Jaques Civetta, France
465mm Dobsonian, fibreglass construction
Doug Tanaka, USA
12.5” F/6 String-Truss Dobsonian
Michael Koch, Germany
8” F/4 “Folding Ruler” Airline Travel Scope