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Welcome to the home page of the 1100 mm Cruxis Telescope.
This telescope is designed and constructed by the Belgian amateur astronomer Robert Houdart and
should see its first light in 2008-2010-2011 2012.
On this page you can follow the progress of this ambitious telescope project.
The actual construction of the telescope started in April 2007, but was interrupted for
nearly 4 years because of problems with the production of the cellular mirror blank.
After Wangsness went out of business in 2010,
it was decided to replace the original cellular blank with a classical, solid Supremax mirror blank.
Mike Lockwood delivered the finished 1100 mm mirror in May 2012, and the construction can now continue.
Latest News May 9, 2012: A new start for the project!!
The 1100 mm Mirror Completed
It's been a challenging ride for the project.
After keeping us waiting for 3 years, the supplier of the 1100 mm cellular mirror blank Wangsness
went out of business in 2010.
As no other supplier of cellular mirrors was available, we finally decided to abandon the ambitious
plan of using a cellular mirror, and instead go for a classical solid mirror blank.
Mike Lockwood procured a 1100x58 mm Supremax blank in mid-2011 and proceeded with the production
of the finished mirror beginning of 2012. The mirror was coated by by OMI and finally delivered in May 2012.
After 4 years of interruption the construction of the telescope can now continue.
The focal length of the primary mirror was finally set at f/3.6, about 440 mm shorter than the initial f/4
design from 2007. With the smaller thickness of the primary mirror (58 mm instead of 185 mm), the eyepiece
height will be 560 mm lower than the original plan.
The change in the mirror design requires a number of changes in the mirror cell, and also influences
the balancing and the height of the telescope. I hope to be able to reuse most of the hardware that
was fabricated nearly 5 years ago...
A Big Thank You to Mike Lockwood
There is no doubt that without Mike this project would not have continued.
His professional attitude and solution-seeking approach has pulled me through the several years during which we
were waiting in vain for Wangsness to produce something.
After Wangsness' failure, Mike readily accepted the financial responsibility and went on to find
alternative solutions.
Thank you, Mike.
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").
The Cruxis Telescope will become one of the largest portable amateur telescopes 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/3.6.
At f/3.6 a 31 mm Nagler with Paracorr (equivalent to a 27 mm eyepiece), will give an exit pupil of just
above 7 mm and provide a 150X magnification for a 32' 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 3.75 m zenith height of the Cruxis Telescope will require a 2.4 m (8 ft) ladder
with 10 steps. The most annoying aspect will be the weight of the ladder, around 20 kg (45 lbs).
Observing will become a good workout!
Optics
[The information in this section is not up-to-date. The cellular mirror has been replaced with a classical
solid Supremax mirror. This information will be updated soon.]
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")
- Primary Mirror Focal ratio: f/3.6
- Primary Mirror Focal distance: 3960 mm (13 ft)
- Primary Mirror Weight: about 105 kg (230 lbs)
- Secondary Mirror Minor axis: 200 mm (8")
- Central Obstruction: 19 %
- Length of truss tubes: 310 cm (10'2")
- Diameter of altitude trunions: 156 cm (61")
- Eyepiece height at zenith: 3.75 m (12')
- Total weight of the telescope: about 270 kg (600 lbs)
- Lowest usable magnification: 150x with 32' 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 30 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.
- 2004-2008: 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.
- The telescope has since then seen another rebuild, with a new, high-quality 16" f/5 Lockwood mirror.
The 35 mm thickness of the new mirror makes it more suitable for short sessions focused on
visual planetary observations mostly of Mars, Jupiter and Saturn.
- 2006-2012: 1100 mm f/3.6
- 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.
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".
Since 2009 I've also created the Chess Engine Houdini, currently the strongest chess engine in
the world. If you're interested, see the Houdini Chess Engine page.
Houdini got created during the long and fruitless wait for the cellular mirror of the 1100 mm telescope :).
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Latest News May 9, 2012: A new start for the project!!
