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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Whole Horizon Mirrors
From: Geoffrey Kolbe
Date: 2011 Apr 25, 07:06 +0100
From: Geoffrey Kolbe
Date: 2011 Apr 25, 07:06 +0100
At 20:44 24/04/2011, Gary wrote:
Ya-but.... When using a telescope of reasonable power only half the light input to the scope is coming from the star and half from the horizon, so there should be no difference whether whole-horizon or split-mirror horizon mirrors are used.
I can see that when using a sighting tube the eye will see an uninterrupted view of the horizon on one side and of the star on the other. For low power sighting systems the images will not be super-imposed with a split mirror system but at least you will see the star.
But.... When trying to see faint stars, it would be better to avail yourself of the increased light gathering power of a telescope - would it not? In that case, does it matter which system you use?
Geoffrey
50% throughput, on the average for both the horizon and the star for the whole horizon mirror. But for the split mirror almost 100% throughput of the dim horizon and almost 100% reflected of the dim star.
Ya-but.... When using a telescope of reasonable power only half the light input to the scope is coming from the star and half from the horizon, so there should be no difference whether whole-horizon or split-mirror horizon mirrors are used.
I can see that when using a sighting tube the eye will see an uninterrupted view of the horizon on one side and of the star on the other. For low power sighting systems the images will not be super-imposed with a split mirror system but at least you will see the star.
But.... When trying to see faint stars, it would be better to avail yourself of the increased light gathering power of a telescope - would it not? In that case, does it matter which system you use?
Geoffrey
