What should be used to periodically dust the exposed lens surface of an eyepiece?

Using a camel hair brush to periodically dust the exposed lens surface of an eyepiece is advantageous because camel hair brushes are known for their gentle and effective cleaning properties. The soft bristles are less likely to scratch the delicate lens surface compared to other materials. They effectively remove dust and debris without leaving fibers or particles behind, which is crucial for maintaining the optical quality of the eyepiece. This method is especially appropriate for sensitive lenses where preserving the integrity of the surface is essential for optimal visual performance.

Other options, while they may seem viable, carry certain drawbacks. A cotton cloth can be too abrasive, potentially scratching the lens if any dirt particles are present. A microfiber cloth is generally safe and effective for cleaning lenses; however, it is primarily designed for wiping rather than dusting. A feather duster, while it may remove loose dust, does not effectively capture particles and may also leave behind feathers or debris. Therefore, the use of a camel hair brush is the most suitable choice for this purpose, ensuring both safety and efficiency in maintaining the eyepiece.