how accurate are those telescope programs?

Question

how can i make a tracking program for the sun and have it control 8 different electric motors constantly (trying to keep a lens focusing sunlight all day)

Answer 1

Long-exposure tracking usually involves using a guide star for feedback. Depending on how precise your mechanics are and how closely you need to track, you might be able to get by running open loop. Otherwise, you could pick off a portion of the solar image (the reflection off a piece of plain glass will do fine) and build a simple feedback circuit with a few photocells: solar image drifts left, apply current to the appropriate motor to move it right.

Answer 2

The programs that control "GOTO" telescope are quite accurate. However, each program is usually designed to fit one particular set of motors: one driving the Right Ascension drive, the other driving a declination motor.

If you were able to design your own program with the equivalent precision, you'd let the sytem continue all night and, the next morning, your lens would resume focussing sunlight.

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I tried to find a program description but no one shows the details. (I found lots of sites selling such programs by using keywords: GOTO telescope tracking program)

If you are satisfied with steady tracking for one to two hours, you could build a "Poncet" table.

Base table is inclined along the north-south line by an angle equal to your latitude. Once set up, the plane of the table will match the equatorial plane (it will be parallel to Earth's equator and perpendicular to Earth's rotation axis.

A secondary table, sitting on the main one, is inclined by an angle equal to the declination of the object you want to track.

All you need is a motor that turns the whole thing at a rate equal to the diurnal rotation:

15 degrees per hour for the Sun

There are a few web pages on this.

Given you objective, it is probably possible to use a "gnomon" approach: A rod that makes an ancle, with the horizontal, equal to your latitude and slanted towards your elevated pole (the north pole if you are in the northern hemisphere).
In other words, the rod is perfectly parallel to Earth's axis of rotation; the rod points to the pole (at night, you'd see that it points very close to the pole star if you live in the northern hemisphere).

On that rod, a movable support that can be adjusted to the declination of the Sun. If a support rod with a fork mount to hold the magnifying glass, then the support makes an angle of 90˚ - DEC with the main rod.

You would only need a motor that turns the rod at 15˚ per hour. In the morning, you point the apparatus to the Sun -- making sure the main rod points to the pole and the secondary support makes the correct angle calculated from DEC. Then your lens will stay pointing at the sun all day.

For greater accuracy, you may want a second motor to control the DEC angle, as the sun's declination changes during the day. Maximum rate of change is near equinox (March and September) where it reaches 24' (0.4 degree) per day.

Answer 3

It's not that hard. Using a little trig, and knowing the exact direction the earth is turning, it's pretty easy to program when you have a database with every object's coordinates.