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[ATM] The 16 inch ultra thin

The weather and my own ignorance of the process has been in the way of
any kind of meaningful star test of the 16.  This is the original
slumped mirror, f3.5, 16 inch diameter, 5/16ths thick, that I got back
from Alcoat last week.  By chance I just found a sucker hole and so
grabbed the scope and a couple of eyepieces.

The scope is mounted in a styrofoam tube.  The mirror box is plywood.
The secondary is 4 inches and should really be recoated, but it has an
OK coating on it. The focuser is an old Meade plastic dismount that
wobbles a bit as the tube is moved by the gear.  The low power eyepiece
is a Dobson special, a 35mm binocular eyepiece.  The second is a 10mm
meade 4000 series Super Plossl.  Relative power is about 40 and 140
respectivly.

The Meade was first in the focuser.  I had pronounced coma away from the
middle of the field.  Also some astigmatism near the edge of the field.
Stars in the middle were blobby.  I don't know if this is a bad figure
or lots of moisture in the air.  There was quite a bit of twinkle.
Still, the sharpness was lacking.

The low power eyepiece gave great wide field views.  Stars were dots, a
bit fuzzy at the edge, no coma to speak of.

I did not try to do a star test in the classic in and out of focus
Suiter style.  I was battling bits of scud crossing the fov and I was
worried about getting the scope in before the next wave of storm came
through.

Test time was about 5 minutes.

I think it will be a good low power scope, perhaps a decent medium power
scope.  It will probably make a good astrocamera.  I am exploring the
idea of doing a cross Gregorian configuration with it.  I think the
extended apparant focal length would help with the coma.  Basic design
specs seem to yield about an f10 afl.

It may test better when it has the chance to come to temperature before
I view.  That is about all of the apology I can offer.

David Davis
Toledo, OR 97391

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