From: "Dwight K. Elvey" 
To: atm{at}shore.net
Reply-To: "Dwight K. Elvey" 


>From: "Bob May" 
>
>The problem with the eye is that as you go away from the KE, the eye lens is
>unable to see all of the cone of light, thus dimming one side of the zone
>over the other.  This isn't too bad near the center but as you go away from
>the  center of the mirror, the light comes to you at larger and larger
>angles which make it easier to vignette some of the light with the edge of
>your iris.
>Basically, what this means is that you pretty much need to get your eye
>closer to the KE in order to see all of the mirror properly.

Hi
 This is a good reason for adding a small low power telescope
to the tester. This is specially true if you wear heavy glasses. You can
not get your eye close enough to the KE with glasses on.
 You could use a small telescope. A cheap rifle scopes work well or
you could make your own. Remember that it is the light that just grazes the
KE that you want. A rectangular hole baffle helps to increase contrast.
Keep the primary as close to the KE as you can. If the scope you use has a
shade or something extending in front of the primary, you should remove
this.
 I haven't been using a scope but only because I've been
too lazy to add one. 3X is a good power for such a scope. Dwight


>As to the point of what is nulled, the blink method works fine as you are
>somewhat doing where both zones go through their shades of gray at the same
>time.  Moving the KE .002-.003" in or out and seeing that one trails the
>other, depending upon the direction will also assist in proving where the
>null zone is.
>Bob May
>http://nav.to/bobmay
>bobmay{at}nethere.com
>NEW! http://bobmay.astronomy.net
>
>
>
>

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