Millennium Telescope

1
Millennium Telescope

• Meeting 2
• Requirements and Design Goals

2
Requirements...
3
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.

4
Mirror

• The mirror spec is fixed the cell must be
  designed to support the 'thin' 19" mirror without
  significantly degrading optical performance.

5
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.

6
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.

7
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.

8
Open Structure

• Avoids fans and promotes rapid cooling of the
  primary. Less prone to wind vibration. Minimises
  weight.

9
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?

10
Stiffness

• Minimise flexure with rigid structures.

11
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.

12
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.

13
Optical System

• Mechanical assembly must be repeatable such that
  telescope is approximately pre-aligned.
• Telescope must be capable of easy remote-site
  fine-alignment.

14
Baffling

• Upper cage and primary mirror baffles need to be
  de-mountable and easily installed.

15
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.

16
Economy of Materials

• Minimise costs by keeping material weight down.
• Use plywood steel where possible and standard
  components if available.

17
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.

18
FAS Website Trawl...
19
John Cross, Bristol AS14 F/4.5 Dobsonian
20
Jim Brace, Wadhurst AS18 F/5 Dobsonian
21
Gary Poyner, Heart of Eng AS18 F/4.4 Dobsonian
22
Wadhurst AS, Norfolk
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Other DesignsAlternative materials
24
Gary Wolanski, USA16 F/5 Dobsonian, 40 Pound,
all-metal construction
25
Gary Wolanski, USA16 F/5 Dobsonian, 40 Pound,
all-metal construction
26
Gary Wolanski, USA16 F/5 Dobsonian, 40 Pound,
all-metal construction
27
Charlie Wicks, USA20 F/4.5 Dobsonian -
all-metal construction
28
Jaques Civetta, France465mm Dobsonian,
fibreglass construction
29
Doug Tanaka, USA12.5 F/6 String-Truss Dobsonian
30
Michael Koch, Germany8 F/4 Folding Ruler
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