Hi everybody
I recently met Mr. Tushar Purohit from IUCAA Pune on his visit to
Aurangabad and got an opportunity to show him the automated telescope
I made. Impressed, he said that he would publish an article about how I
made the telescope, in an international astronomical magazine that IUCAA has
started.
So, here is that article:
I am Anant Kale, student
of class 11, Nath Valley School, Aurangabad. I am interested in astronomy, physics,
mathematics and I wish to pursue higher studies in physics.
The optical tube is a
standard size PVC plumbing pipe attached to the mount using a metal clamp. The
clamp is a 2mm thick steel plate bent into a circular shape with two nuts on
diametrically opposite ends to bolt the supports. The telescope mount is of Dobsonian
design which is simple to make and easy to motorize. The mount is small and
compact with a height of 18 inches. It can be used as an alt-az mount as well
as an equatorial mount. When it is placed on a surface parallel to the ground
it behaves as an Alt-Az mount; when placed on an inclined surface with angle of
inclination equal to altitude coordinate of the pole star, it can be used as an
equatorial mount.
I recently met Mr. Tushar Purohit from IUCAA Pune on his visit to
Aurangabad and got an opportunity to show him the automated telescope
I made. Impressed, he said that he would publish an article about how I
made the telescope, in an international astronomical magazine that IUCAA has
started.
So, here is that article:
“Making of a goto telescope”
I got
interested in Astronomy after joining the astronomy-club in our school which
involves students in activities such as star-gazing, watching special celestial
events and making telescopes. I would specially like to thank my physics
teacher Mr. Suryavanshi because of whom I was able to attend a telescope making
workshop in IUCAA Pune.
Last summer,
I set out to make a low cost, fully automated, ‘goto telescope’ using a 100mm
diameter primary mirror with a focal length of 650mm. It has full ‘goto’
capabilities and can be operated using any smart phone, laptop or tablet pc.
The user can
enter coordinates in altitude-azimuth form or equatorial form using a smart
phone or laptop and the telescope will slew to the desired coordinates. The
total cost of this telescope was approximately Rs 7,500 and took 2-3 months to
make.
The primary mirror was made at a mirror making workshop in
IUCAA, Pune, under the guidance of Mr. Tushar Purohit. After manual grinding
and polishing the glass for about 20 hours, the integrity of curvature of the
mirror was tested using ronchi test and the mirror was coated with aluminum.
The brightness of images formed in a telescope is proportional to the square of the aperture. Thus it is exponentially more difficult to locate faint objects on small telescopes. Goto capabilities are thus very valuable for amateur astronomers using small aperture-telescopes. They enhance the viewing experience by eliminating the time and effort often spent in locating objects of interest, in the polluted urban skies.
Making the telescope was an enjoyable and informative experience. It helped me learn many things about telescope-making, optics and electronics.
To motorize
the telescope, high precision stepper motors were used for both axes (14PM-M201
MINEBEA CO. stepper motor, 200 steps per revolution) giving an accuracy of
0.075°. All the electronics are controlled using a microcontroller Arduino Due.
The Arduino series microcontrollers are versatile and easy to use. They can be
programmed using C++ language. They can receive inputs from sensors, serial
monitors or computers and give desired outputs. The Arduino Board was programmed
to receive the coordinates of the celestial object as input from a laptop or
even smart phone.
The microcontroller calculates the number of ‘steps’ that the
stepper motor has to rotate depending on the step angle and gear ratio and
sends the corresponding output to a motor driver. In this case there are
200*25/360=13.89 steps per degree. The motor driver comprises of a dual
H-Bridge integrated circuit(L298). It provides the necessary power gain to the
output from the Arduino. As the motor rotates the telescope slews to the
correct coordinates.
For the altitude/declination
drive, a stepper motor with a worm gear pair of gear ratio 1:25 was used. The
slew speed was set to 2 degrees per second. However there were several
difficulties while making the azimuth/RA drive as it required a significantly
more powerful motor while maintaining precision. The first attempt using the
same stepper motor with a worm gear was not satisfactory as it could not
provide enough torque. In the modified design, the drive will be provided to
the circumference of the telescope instead of the axis thereby reducing the
torque-demand.
For convenience and ease of use, a hand-held
controller was added to operate the telescope manually. This is very useful when
the coordinates are not known and to make finer corrections to compensate for
drift.
This whole
telescope making experience has been very instructive and enjoyable and has
further increased my interest in astronomy. I hope to set out on bigger and
better projects in the future.
PICTURES TAKEN FROM MY TELESCOPE