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The RA setting circle is of little use to a beginner on most mounts. It has two scales one for RA and one for Sidereal time. The idea is that you set the sidereal scale so that your current sidereal time is aligned to the meridian (straight up). Then the other scale will read the RA of the object.
If the setting circle could be made to follow sidereal time you could set your RA from the other scale. However the setting circles usually move with the RA so all you can do easily is read the sidereal time of the object you have set the scale to.
The Dec scale is slightly easier to read but it also has two scale reference points When one is set to 90 deg the other will read the declination. On the whole it is rather messy unless you have pecision scales and vernier controls that allow you to set and read to at least an arc minute.
Barry
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