Last updated: 21 May 2008
Subject:	Adaptative Optic for ETX90 (The First Experiment)
Sent:	Tuesday, May 20, 2008 00:22:05
From:	Fernando Lamarca (
An other device for ETX90 from Zaragoza, Spain (Expo 2008).. 

Tired of vibrations in the telescope????? , yes ...... here, the

Two types of adaptive optics exist

The good System, tries to resist the optical differences of the
different layers from the atmosphere, being based on the deformation of
a small mirror to prepare the wave front that arrives.he is expensive
and complex

The other method, tries to annul the vibrations caused by action of the
wind, for example, and it is based on shaking one's head a mirror in
x-axis and to annul to these vibrations This second, it is the chosen

Basically it consists of resisting the vibrations that take place in the
telescope with an electronic system able to make vibrate a mirror in
contrast to the vibrations read by an accelerometer

I explain myself.

An accelerometer catches the subtle vibrations that appear mainly in a
telescope due to the wind These vibrations are turned to tension by this
accelerometer with the advantage to have differentiated x-axis and the
axis and (two legs different from the integrated one). These signals are
processed and they are injected in sense in opposition to the original
vibration, to a mechanical system that consists of two small
electromagnetic actuators that vibrate to the rate of the vibrations
caught by the accelerometer, one in each axis and which they are shared
in common of a small platform in suspension that takes to patch a
mirror.(Sensitivity of the system) adjusts to the level of vibration by
means of two potentiometers and the result is the cancellation of these
vibrations by mechanical action on the mirror.

Seems simple, truth? , because it is not it, the mechanics is extremely
delicate as you can see in the photos and the system must be perfectly
fit so that he is effective, but, the result is that it even vibrates
but To different increases, different adjustment

Even it is left much work on the matter, but it is a great step to
obtain a smaller and more powerful adaptive optics.

In order to understand the assembly:

First I make affect the mirror a laser beams that will serve me to
calibrate and to value the obtained improvements.

With the apparatus extinguished, I slightly strike the box that contains
the OA system (ptica Adaptativa)

The result is that the laser opposite draws in the wall of a chaotic
figure as resulting from the vibrations that appear in both axes.

I connect the system and I strike again, more or less equal, the small
box of the OA. When resisting the system the vibrations produced by the
tap, the result is that the figure that More or less draws the laser
this diminished enough (nonprecise but him lack little) works! , before
these vibrations, the mirror is able to resist the vibratory movement of
the set

Even it is left much to walk, to put everything in the size of a prism
of 45 degrees, a robust electronics but and with less calibration and to
suspend the mirror of an effective way but ..... Not that I seem giving
taps to the box and watching crazy the wall? .

At the moment, the improvement measured in the quality of the image is
even a little lowers, is necessary to reinforce the mechanical
sensitivity of the system and to improve the phase angles that appear in
the signals of both axes and a length et cetera

I obtain a benefit of a 60% more or less as far as cancellation of
vibrations (vibrates a 60% less) but not always with himself that annul
the vibrations to me (3 of every 10 times with himself), sometimes
autofeedback and becomes crazy, others does not seem to find out as it
is its work! and others work very well.

Everything will be walked safe

If somebody has some suggestion.


PS: that show with the tripod of the telescope, the laser and the device
in half of the street doing tests the neighbors must be hallucinated,
everything is by Astronomy
Fernando Lamarca Belanche
Fernando Lamarca Belanche
Development Engineer
R&D On-Board Systems / CAD Area
Zaragoza 50.057       SPAIN 




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