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Message: <blockquote data-quote="Binastro" data-source="post: 3183063" data-attributes="member: 111403">. Hi David,I don't think that the position of putting three neutral density filters in front of the objectives or behind the eyepieces is of any significance in determining the source of the expanded disc for a very bright object.Either way, you are reducing the intensity to 1/64 of the original.So this in itself I don't think proves one way or the other the source of the expanded disc.However, it may be that the sensor, either film, digital sensors, or our eyes may be the cause of the expansion.Using a camera would not help with a very bright object as the sensor or film would be overloaded and may produce an expanded disc, either smaller or larger or the same size as seen by our eyes.And it may be that different people's eyes produce different sized discs. Even if our eyes focus properly at Infinity.I think that it was may be the Univex Corporation, possibly of New York?, who produced the unusual half frame, sector shutter, Mercury camera, who had up their sleeve a device that could look at the Sun without any glare. My memory is poor, perhaps it used phosphorus?? Anyhow, I don't think they ever found an application for this device.I will have to ask a lens designer friend whether he can advise me on this topic.</blockquote>