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Welcome to the home page of the 110 cm Cruxis Telescope.
This telescope is currently being designed and constructed by the Belgian amateur astronomer Robert Houdart and
should see its first light in 2010.
On this page you can follow nearly real-time the progress of this ambitious project.
The actual construction has started in April 2007.
Latest News October 24, 2008: Patience is a virtue
With the mirror blank now more than 12 months overdue, patience appears to be the most important quality in building a big telescope!
June 2, 2008: Updated schedule for 1100 mm mirror blank
After having solved some design and thermal cycle problems that have stopped everything else, Wangsness is going forward again.
A realistic time window of 3 months is now scheduled for casting the cellular mirror blank.
March 16, 2008: Waiting for the 1100 mm cellular mirror blank...
First scheduled for October 2007, then moved to January 2008, the casting of the primary mirror blank seems to take quite a bit longer
than orginally planned. Currently there is no further information from Wangsness about a likely date for its availability.
I do not really mind the waiting, but find the lack of information and the unpredictability of the situation quite annoying.
Let's wait and see...
February 26, 2008: Coated secondary mirror arrives!
A package from Mike Lockwood arrived this morning - containing the coated 200 mm secondary mirror and a new 16"x1.4" f/4.9 mirror
for the 16" motorized alt-az telescope (that page now really needs an update!).
The coating of both mirrors was done by Spectrum Coatings and looks absolutely perfect.
February 17, 2008: NEW Mirror Cooling Calculator
Another spinoff of the design work on the 110 cm telescope, the
Mirror Cooling Calculator for telescope mirrors is made available.
January 22, 2008: A telescope in the nursery room
The structure finally begins to look like a telescope!
More information about the latest updates on the following pages:
- The completely revised Mirror Cell page featuring the 54-point floating point cell and
the double cable sling edge support.
- The Mirror Box page featuring the design of the mirror box, the mirror cell,
the truss tube connections, the 7-fan ventilation system with air distribution headers.
- The updated Truss Frame page with details about the truss tube selection, truss
tube attachments, and deformation plots of the telescope in horizontal position.
With the mirror cell, ventilation system and truss tubes finished, all the pieces of the puzzle are falling nicely into place!
Tourism of the Deep Sky
I'm an avid deep-sky observer and spend nearly all my holidays observing at my favorite site in the French Alpes de Hautes Provence
not far from the famous Mont Ventoux. My home town Leuven in Belgium (about 25 km east of Brussels) has way too much light pollution to do any
serious deep-sky observing.
After having constructed a 406 mm (16") scope in 1990 and a 635 mm (25") in 2000-2002, I naturally wanted to move on.
Since 2005 I've been contemplating the "next" telescope. I finally decided to go for the
biggest scope I could fund and manage by myself, which turned out to be 1100 mm (43.3").
The Cruxis Telescope will become one of the largest portable amateur telescope in the world, together with
Erhard Hänssgen's 107 cm Dobson (42") and
Dan Bakken's 41.2" Hercules (1046 mm).
What drives me in this venture is the extra-ordinary splendor of the universe one can experience at the eyepiece.
Objects like the Orion Nebula, the Whirlpool Galaxy or the Veil Nebula are beautiful beyond description in large telescopes.
Photographs simply do not do justice to the visual thrill
at the telescope eyepiece (although they may show a lot more details than you could ever see visually).
The best description of my favorite hobby would be "tourism of the deep sky".
Design Criteria
- Single person transportation
- I will quite often have to transport the 270 kg (600 lbs) scope by myself. By no means can or do I want to lift something heavier than about 25 kg.
This is basically not very different from my 100 kg (220 lbs) 635 mm scope. I'll either have to use a trailer or buy a van that is big enough to roll the
scope in.
- Single person set-up in 30 minutes
- Assembly should be possible by a single person in about 30 minutes. The upper cage will be too big and too heavy to be mounted on top of the ladder, so a
system must be provided to mount the upper cage while standing on the ground.
- Alt-azimuth motor drive system
- This will not be a Dobsonian telescope! There won't be any teflon bearings, nor will the scope be hand-moved.
At a total weight of about 270 kg (600 lbs), I felt it was probably not a good idea to rely on manual pushing and pulling around.
- To control the scope movements, I do not want to use a laptop; computer screens hamper the dark adaptation required for the best
visual deep-sky observing. Furthermore, with the eyepiece up to 4 meter from the ground, a wireless handpad is a must.
 Visual observing only- Initially this scope is intended for visual observations only. This said, the secondary mirror has been designed to give full illumination
of a 38 mm (1.5") field, so later photography will be possible.
- To enable long-exposure photography, a field derotation unit will be required.
- Focal length (height of the telescope)
- 15 years ago large Dobsonians where typically at f/5, nowadays amateurs are frequently using telescopes as fast as f/3.
- Taking into account considerations like eyepiece height, size and weight of secondary (a crucial factor in the total weight of the upper cage)
and Newtonian coma I decided to go for f/4.
At f/4 a 31 mm Nagler with Paracorr (equivalent to a 27 mm eyepiece), will give an exit pupil of just below 7 mm and
provide a 160X magnification for a 30' field of view.
- As for the height, I've never felt uncomfortable observing with a ladder. The 635 mm (25") f/5 requires a 6 step ladder to reach zenith, and in my experience
you simply tend to forget that you're observing on a ladder. The 430 cm zenith height of the Cruxis Telescope will require a 270 cm (9 ft) ladder
with 10 to 12 steps. The most annoying aspect will be the weight of the ladder, probably around 20 kg (45 lbs).
Observing will become a good workout!
Optics
Mike Lockwood will take on the challenge to produce the optics for the Cruxis telescope project. Mike is an experienced and
well known amateur telescope maker who has transited into custom, high-quality professional optical work for mirrors up to 50" (127 cm).
The picture on the right shows Mike holding the secondary mirror blank at its arrival in October 2007.
To reduce weight and improve the cooling time of the optics, both the primary and secondary mirrors will be cellular. The cellular mirror blanks are
designed and cast by Wangsness Optics. I will validate the cellular designs
of the mirrors by finite element analysis.
The optical surface of the primary mirror will be approx. 15 mm (5/8") thick, its total thickness about 185 mm (7.3").
More information about the cellular design of the 120 kg (260 lbs) primary mirror will follow later.
The Secondary Mirror Design page contains more information about the 1.9 kg (4.3 lbs) secondary mirror.
Delivery of the finished optics is scheduled for April 2008.
Construction
Some Facts and Figures
- Primary Mirror Diameter: 1100 mm (43.3")
- Primary Mirror Focal ratio: f/4
- Primary Mirror Focal distance: 4400 mm (14 ft 5")
- Primary Mirror Weight: about 120 kg (260 lbs)
- Secondary Mirror Minor axis: 200 mm (8")
- Central Obstruction: 19 %
- Length of truss tubes: 370 cm (12 ft)
- Diameter of altitude trunions: 154 cm (61")
- Eyepiece height at zenith: 430 cm (14 ft)
- Total weight of the telescope: about 270 kg (600 lbs)
- Lowest magnification: 160x with 30' field of view
Mechanical Design
Design and Construction History
For brevity only the most recent news are shown below.
Click here to view the full history of the Cruxis telescope.
- September 27, 2007: MirrorMesh3D
- More information about MirrorMesh3D, the automatic
mirror model generation for 3D analysis of telescope mirrors.
- November 5, 2007: Mike Lockwood has finished the secondary mirror
- The surface of the mirror is fully polished, scratch and sleek free and quite smooth. It is very flat along the major axis.
Fringe images show that the over-all accuracy is better than 1/8th wave at 550 nm. A real beauty!
- November 26, 2007: NEW Mirror edge support calculator
- A spinoff of the design work on the 1100 mm cellular mirror, a
mirror edge support calculator for Dobsonian (alt-azimuth) telescopes is made available.
- January 8, 2008: Mirror box under construction
- Happy 2008! With the design of the primary mirror finalized, the actual construction of the telescope structure can now continue.
The first pictures of the mirror box under construction are available. The inside of the mirror box is 1160 mm square leaving 25 mm around the mirror.
- January 22, 2008: A telescope in the nursery room
- The structure finally begins to look like a telescope! More information in the following pages:
- the completely revised Mirror Cell page featuring the 54-point floating point cell and
the double cable sling edge support
- the Mirror Box page featuring the design of the mirror box, the mirror cell,
the truss tube connections, the 7-fan ventilation system with air distribution headers.
- the updated Truss Frame page with details about the truss tube selection, truss
tube attachments, and deformation plots of the telescope in horizontal position
With the mirror cell, ventilation system and truss tubes finished, all the pieces of the puzzle are falling nicely into place!
- February 17, 2008: NEW Mirror Cooling Calculator
- Another spinoff of the design work on the 1100 mm telescope, the
Mirror Cooling Calculator for telescope mirrors is made available.
- February 26, 2008: Coated secondary mirror arrives!
- A package from Mike Lockwood arrived this morning - containing the coated 200 mm secondary mirror and a new 16"x1.4" f/4.9 mirror
for the 16" motorized alt-az telescope.
The coating of both mirrors was done by Spectrum Coatings and looks absolutely perfect.
- March 16, 2008: Waiting for the 1100 mm cellular mirror blank...
- First scheduled for October 2007, then moved to January 2008, the casting of the primary mirror blank seems to take quite a bit longer
than orginally planned. Currently there is no further information from Wangsness about a likely date for its availability.
I do not really mind the waiting, but find the lack of information and the unpredictability of the situation quite annoying.
Let's wait and see...
Personal Telescope History
- 1981: 114 mm f/7.8
- I started my observing career as a 13-year old in 1981 with a 114 mm Newtonian (4.5"), a standard newbie telescope at the time.
- 1990: 406 mm f/5
- My first home-made scope saw the light in 1990; it was a 406 mm (16") f/5. I was inspired by the Sky & Telescope article "Hawaii-bound pocket scope"
by Tom Clark from Tectron Telescopes. The optics were purchased from Galaxy Optics.
- 2000-2002: 635 mm f/5
- Around 2000 I started designing and constructing a 635 mm (25") f/5 telescope. Finished in May 2002, it's a very fine telescope, with great
optics from OMI.
- 2004-2005: Complete rebuild of the 406
- Since 2004 I have completely rebuilt the 406 mm, using some ideas from Mel Bartels.
The result can be seen here.
- 2006-2008: 1100 mm f/4
- The current project.
Professional Background
I am a mechanical engineer with a soft spot for mathematics and software development.
From 1991 to 1999 I was employed by Tractebel Engineering to analyze
earthquake and impact resistance of nuclear piping systems. You can see some of the products I worked on
in this web site for EditPipe.
Since 1999 my main activity has been the design and development of two web-based CRM applications:
first eLink, and since 2005 Efficy. The latter application has been selected by the
IT magazine Data News as one of the "Top 10 Products for 2006".
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