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The whole bak7 vs. bak4 issues has been beat to death by the binoviewers people so it was very odd to see it debated here.

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As long as there are Newbies, you will see it again and again. As we grow, we get excited about NEW discoveries that have been known by the Oldbies for decades. It the nature of the beast. Hey, let's talk about metal mirrors, optimizing our Newtonian, or builing a research-grade telescope based on an f/1.75 shaving mirror from Wal-Mart.

For the fellow who has known people who can tell the difference in brightness between Bk7 prisms and BaK4 prisms, I would like to say that I think it is more in the differences in blackening, baffling, and field stops, than in glass types. When it comes to optics, things are not always as easy to pin down as it first may appear. But then, that's just my opinion.

I can place a 1.5-in, black suction cup over one obj. of a 7x50 (Obscuring 75% of its surface) and most folks will not know the difference. This is not opinion. It is test results.

Also, some are using the names BaK4 and Bk4 interchangeably. They should not.

In d light, BaK4 has an index of 1.56883
and
In d light, Bk3 (Bk4 is not in my Schott catelog) has an index of 1.49831.

Just some thoughts.

Cheers,

Bill

Edited by billcook (09/18/05 02:51 PM)

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