X-Message-Number: 19492
Date: Fri, 12 Jul 2002 16:38:56 EDT
Subject: Intensity interferometer 6, reading brains in ten years?

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Building a first imaging intensity interferometer - i cube- is a big project. 
The give me $ 100 millions and I build it is not an option. some thinking 
must be invested in the way such an instrument could be made in an 
incremental way. I suggest three steps:
1/Observation of star ocultation by asteroids.
2/Observation of lone planets (planetars) in interstellar space.
3/Use of the instrument in i-cube mode.

1/ Everybody know about solar eclipse by the Moon. In the same way, stars are 
eclipsed by asteroids, the common term is then ocultation. In this 
phenomenon, the shadow of an asteroid move at the surface of Earth. The 
position of the shadow track defines the precise orbit of the asteroid, the 
track width gives the asteroid diameter perpendicular to its trajectory (most 
are not spherical). The asteroid shadow is not clear cut, there are 
interference fringes on its border. If high speed photometry is used, the 
starlight oscillates at start and end of ocultation. These fringes with the 
known position of the asteroid give a way to mesure the angular diameter of 
the star. If the true diameter is known ( from physical considerations) then 
this give a direct mesure of the star distance. This may be checked 
independently if fringes can be observed in different colors ( at least 3). A 
fringe observer telescope for ocultation of bright stars would have a 
diameter near 1 m (40"). A color discriminating system would have a diameter 
in the 80" domain. Up to ten such mobile instruments would have to be lined 
up perpendicular to a predicted shadow track. This number is necessary to 
take into account the error margin in track position and to mesure the track 

At this point, we have a first batch of observing, mobile telescopes with 
single point high speed photometers. When that system has been built, it can 
be paid by organized travel for interested amateur astronomers. Potential 
custommer can  be recruited through organisations such Iota, IAPPP, AAVSO,...

2/With more telescopes, dark planetars can be detected. As in the first case, 
stars are oculted by dark bodies. The difference is that we don't know which 
stars and when. Millions of stars must then be monitored continuously with 
high speed photometers. The difference with what is requested for i-cube is 
small, mostly at the software level. What is interesting, is that there is a 
pending offert to pay for the electronics part of the system if someone pay 
for the optical part. Exploiting the step 1 system could pay for a telescope 
making workshop. There is at least one organisation, TASS, giving hardware in 
exchange for astronomical software writting. A similar scheme could be used 
(may be with TASS programmers!) giving travels and observing time in exchange 
for i-cube software making.

I think it would be interesting if someone could pick up that project. Well, 
I know, everybody out there has its own project, problems, investment plans 
and so on. I am not in the best position to make this myself, but I can 

I have been interested for some time into astronomical photometry. I had a 
small telescope for some years, I am converting it into a robotic system, 
computer operated. Near the end of that year I plan to adapt this automatic 
working to a larger 30" instrument. The 30" scope is the first try in a batch 
of 38" scopes, I have the raw glass disks for the first two, beyond a second 
30". The 38" mirror blanks must be "cooked" before polishing, I have 
completed in June a special one square meter oven for that. A single 
excentric polishing machine for one meter mirrors is two week from 
completion. Unfortunately, it is 400 mi. from my work place, so I can't 
complete it as fast as I would like. Next year all will be in place to 
produce one meter telescopes, a project I am after for nearly 10 years.

I have a second polishing instrument, a double excentric for two meters 
mirrors. It needs some adjusting yet to be run at full capacity. The main 
problem yet is to buy blank mirrors of that size. Because they are too 
costly, I move towards making these large disks myself. I have started work 
on a 2.3 m  (7.5') kiln with a rotating mold for spincast honeycomb disks. 
The first mirror could be ready for polishing two years from now. The main 
problem yet is to have the time to work on these projects. Either, I must 
quit my current work or I must relocate my workshop. The definitive choice 
will be made this Autumn.

The calendar could be that: First ocultation observing in 3 years, then 5 
years to produce 100 instruments in the 2 m class. In 2010 the first i-cube 
would be running at full power and all the elements would be at hand to make 
a phonon system. On the other hand, a small group with some money could 
target directly the end system and build a phonon brain reader in two or 
three years. Can anyone do that?



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