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Old 10-10-2020, 09:54 AM
brian2014
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Join Date: Sep 2014
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Testing an Eq Platform

I built a platform a few years ago and developed a fairly simple test procedure.

Set your platform up about 3 to 4 metres from and parallel to a wall.
Make a bracket up for a laser collimator to point at the wall and square to the centreline of your platform.

Start your platform running and every 10 minutes mark a cross on the wall from the laser collimator.

After 1 hour you will have a line of dots on the wall.
End to end distance represents represents one 24th of 360 degrees of travel, which is 15 degrees. Measure the distance to the wall and some high school trig gives you your measured angle. So you can adjust your motor speed to match. Star checking is still the best way, but it found this method gave very good results.
If you measure the 10 min gaps you tell if your platform is slipping.

If you look at the vertical angle the line of spots makes on the wall, it represents latitude the platform is working at. You can then adjust the level to suit your observing site.

Daylight Polar Alignment.
I found using a compass was to inconsistent, so I use this solar method.
Mark a centreline on your base board. Before dark, do an initial setup of the base board. Get a plastic protractor and align it to your centreline. Find something to act as a vertical post with a sharp edge(a builders square works well) and position it at the centre of the protractor. You should now have a nice shadow falling on the edge of your protractor. I then open up Sky Safari under search select the Sun. You can get up a page called Object Info. On that page under Celestial Coordinates is the current Azimuth of the Sun. Have a look at your protractor, if you are polar aligned your shadow line on the protractor should match the current azimuth of the sun. Adjust as required. I estimate I can align to better than a quarter of degree, which is all you need for visual observing. A bigger protractor will give a better result if needed.

Hope this helps. Have fun.

Brian
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