[mental4astro (Alexander)]

There is discussion about the Encke Minima. It is a valid point. The problem with the Minima is would we be able to pick up the subtle dynamic range variation on the brilliant rings. Considering how thin/narrow these features are, I would struggle with the minina.

A third possible thing could be the combination of the Division combined with the outer edge of the Minima which sits beside the Encke. Then here is a slightly, oh so slightly wider space, and only the Division itself added the necessary contrast. But this feature is still exceptionally thin. Seriously thin!

I like the challenge to the claims of having seen the Encke Division. Don't forget i did not see this alone, and the Encke's size does fall within a range of factor that is a plausible % of the Cassini Division to be detected. 1/14th part of the Cassini Division, a feature that is not dimension-less, but a measurable span of 0.65", which should be just about imperceptible for an 8" scope, but it is a thick line. This is certainly a possible fraction of the span of the Cassini that can be detected by the human eye - something that I back my vision for. Nor did I say that the Encke was an immediately noticeable feature. It isn't. It was even then a freaking difficult thin line to detect.

I have also spent hundreds of hours with the Moon, so my eyes have learned how to pull detail from a very high contrast situation. On many occasions I have shown very fine lunar and planetary features to others yet those features remained invisible to them, either their scopes were not able to resolve the features or their eyes could not pick them up.

That Nick and I saw it, or thing related to it, I still don't doubt. The feature was exceptionally thin. That what we saw was an exceptional feature, I completely agree. It was not on one occasion that we saw this, but two separate nights. So it was repeated. Therein lies the challenge that presents the Encke Division.

There are two lunar features that I can compare this to. There is a very thin rille that runs along the floor of the Alpine Valley and another down the sinuous Vallis Schroteri. The latter is particularly difficult. These two internal rilles are near equally difficult to detect as the Encke. What most helps with these rilles is there are two parts to them - the dark edge shadow beside the highlighted opposite face. The Encke is just the thin black line with no highlights to set it off. Spot these two lunar features, and you are well on your way to detecting what we saw. The black shadow line of the rille in Vallis Schroteri, THAT line is at the same scale as the Encke Division!

Below are two screenshots from Virtual Moon Atlas of the two vallies, Apline and Schroteri. The rilles in question run down the inside of the main channels. These thin internal rilles are very fine features.

Alex.