Re: Pier height selection help needed...


mogulskier_groups
 

Hi Jeff,

Wouldn't you be using a diagonal when using it with an eyepiece?
That's my only input :-)

Dave

--- In ap-gto@..., "jeff_crilly" <ne14mx@...> wrote:


Last time for me, I promise. (Btw, I've been thinking of compiling
some dimensions, i.e. eyepiece-height-@-zenith-from-pier-top for
various OTAs on the AP1200 and AP900.)

I'm trying to finalize the AP1200 pier hieght. Either 42" or 48"
is
appropos for me -- the downside w/ 48 is that the saddle might be
too
high to easily get a 30 lb OTA up there. Otoh, if 42" is too
short,
I'll be crawling on the ground at zenith.

I did a bit of estimating, and some math...

Zenith is the worst case, so assuming the DEC is horizontal, the
center of the DEC shaft looks to me to be about 10" from the TOP of
the pier.

(I assumed the diameter of the DEC top to be about 7".)

With a 12" SCT, the back of the SCT (including diagonal) is
probably
8" from the center of the DEC axis. (assuming tail heavy SCT.)

This puts the eyepiece about 2" ABOVE the pier height.

So eyepiece height w/ the 12" SCT for 10x42 and 10x48 is around...

42" pier: eyepeice 40 inches above the ground.
48" pier: eyepiece 46 inches above the ground.

Seated comfortably (knees at 90 degrees), I find that 40" requires
the
neck to be bent just a little. (I'm 5'9")

So, I suspect the 42" pier will work w/ the AP1200, and an SCT,
visually.

However, a refractor (right now FSQ) is going to have an eyepiece
height way too low on the 42" pier. (Fwiw, I use the FSQ on an
AP900
w/ a 48" pier and it is ok.)

Its really a tossup for me.. the 42" has the advantage of being
lower
when loading the AP1200 and OTA on it, at the expense of being a
tad
bit too low for viewing at the zenith, which is fairly rare.

Anyone have direct experience?

Am I missing something?

thanks

jeff

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