The result is that no trace of " fiddling " exists, and the movable and fixed webs come sharply together in focus with the highest powers.
It didn't spin webs and looked more to Evelyn like a mutated cat, but the moment she recalled Kiera's fear, she also realized that the cat-like creature would easily pass as a large spider.
One of the most essential points in a good micrometer is that all the webs shall be so nearly in the same plane as to be well in focus together under the highest powers used, and at the same time absolutely free from " fiddling."
To avoid such error Dawes used double wires, not spider webs, placing the image of the star symmetrically between these wires, as in fig.
Other astronomers use the two distance-measuring webs, placed at a convenient distance apart, for position wires.