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What causes the black hole?

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/21/2008 at 22:28
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Optics GrassHopper
Optics GrassHopper

Joined: February/14/2008
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Points: 4
Looking through a scope at high power say 14X getting a sight picture is really difficult unless you are lined up just right. Otherwise it is black. Is this a function of the exit pupil diameter so is this effect worse for smaller exit pupils? So would a larger objective for a given power be easier to get a sight picture?

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/22/2008 at 02:50
8shots View Drop Down
Optics Jedi Knight
Optics Jedi Knight
Lord Of The Flies

Joined: March/14/2007
Location: South Africa
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Points: 5725
The black hole is caused by gravity falling in on itself. No light can escape this dense mass.....Bucky
No, only joking. You have it correct. The larger the power setting for a given objective lense, the smaller the exit pupil becomes. This means that the eye has to be alighned correctly with the line of sight in order not to have the black image.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/22/2008 at 07:09
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Optics God
Optics God
God of Wind

Joined: August/24/2007
Location: North Georgia
Status: Offline
Points: 12082
8 shots simplified the answer, and yes it is correct. there are of course also other factors that can affect this as well. Over all scope design, and the optical triangle I think is how Koshkin puts it. Suffice it to say that some scopes that are of the same power and size are more prone to do this than others are, due to these design parameters.
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