From: "Roger Chisholm-Batten" 
To: "atm" 
Reply-To: "Roger Chisholm-Batten" 


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One matter that I have not seen properly explained in the archives is =
that as a result of the basic Dobsonian design, whilst the altitude =
turning force remains equal wherever the scope is pointing, the =
rotational or azimuth force required when pushing the end of the scope =
varies from minimal when pointing at the horizon to increasingly =
difficult when nearing the zenith.  Moving the tube alone near the = zenith
tends to topple over the scope rather than rotate the tube.

Does one accept this as a design quirk of a Dobsonian or are there =
get-arounds such as a lever/pole sticking out of the base to provide a =
suitable turning force or is Ebony Star & Teflon so malleable that the
= effect disappears? Surely Not?

I noted this a few weeks ago just after my 'First Light' (alas not = kosher
Ebony Star but definitely good grade Teflon).  Looking at Saturn = was a
joy whilst Jupiter near the zenith became a pain after a while.

Roger



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One matter that I have not seen =
properly explained=20
in the archives is that as a result of the basic Dobsonian design, = whilst the=20
altitude turning force remains equal wherever the scope is pointing, the =

rotational or azimuth force required when pushing the end of the scope = varies=20
from minimal when pointing at the horizon to increasingly
= difficult=20
when nearing the zenith.  Moving the tube alone
near the = zenith=20
tends to topple over the scope rather than rotate the tube.
 
Does one accept this as a design quirk =
of a=20
Dobsonian or are there get-arounds such as a lever/pole sticking out of = the base=20
to provide a suitable turning force or is Ebony Star & Teflon so =
malleable=20
that the effect disappears? Surely Not?
 
I noted this a few weeks ago
just after =
my 'First=20
Light' (alas not kosher Ebony Star but definitely good grade Teflon).=20
 Looking at Saturn was a joy whilst Jupiter near the zenith became =
a pain=20
after a while.
 
Roger
 
 

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