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Thankyou Dave, your explanation is convincing. Perhaps the thing to
do is actually stop down the object lens of my theodolite then.

Geoffrey


At 15:20 26/01/2012, you wrote:

>Frank is right about magnification being the important parameter in
>seeing stars during the daytime.
>
>For any magnifcation, a star shows as a point source of light in the
>background of scattered light from the atmosphere. The higher the
>magnification the smaller the field of view and the less scattered
>light is picked up.
>
>Increased objective diameter picks up more starlight but also more
>scattered light, no improvement in contrast.
>
>The higher the magnification, the smaller the field of view and the
>harder it is to find the star but as Frank suggests a computer
>controlled scope will sove that.
>
>Dave F
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