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How to use Setting Circles?
Setting circles are a very useful tool for operating equatorial mounts,
especially for finding faint objects without a GoTo function. They are
best used in combination with a physical or digital star atlas, because
you need to know the RA and DEC coordinates of stars and nebulas.
There are setting circles on both the RA and DEC axis, marked with
celestial coordinates. Both setting circles are manually movable. At
each circle, you can find an arrow pointing to a specific coordinate.
1. To find a faint object, first consult your star atlas and learn about
the region of the sky around the object. You need to find a star in the
vicinity of the object, that you can recognize with your naked eye in
the night sky. This will be your reference star.
2. Point the telescope at the reference star and centre it in a low
power eyepiece. Check the RA and DEC coordinate of this star in your
atlas.
3. Rotate both setting circles so that the corresponding arrows mark
exactly the coordinates of the star. The circles are now set to your
reference star.
4. Check the RA and DEC coordinates of the faint object you are
interested in observing. Rotating the telescope around both axes will
also change what coordinates the arrows are pointing at.
Move the Telescope until the settings circles show the exact RA and
DEC coordinates of your target object
5. The object should now be visible in the field of view of your
telescope (using a low powered eyepiece).
Tip:
This method is more precise
the closer the reference star is to
your target object.
