How To Calculate The
Column And Wall Height
(Note: I like to keep
things simple and effective, for me. There may be a better way to do this,
but, for me, this is the way I did it. Totally based on the viewing height
that is comfortable, for me.)
After trying various heights,
this was the one I felt was best. The tripod legs fully collapsed and the
scope at fifteen degrees which then defines the eyepiece height. .
I use my TeleVue Panoptic
41mm alot. So the basis for the final height was being able to look into the
Finder Scope almost on my tiptoes and and the Panoptic was also at a very
comfortable viewing height. It is the tallest of my eyepieces
Note: All my calcs are
based with the telescope at fifteen degrees to the horizon. An arbitrary number
that felt comfortable for me. After all, below that, the athmosphere really
makes seeing anything very difficult.
Then, we level the scope
Adust the degree wheel
to zero. I marked the spot with tape. The cast in marker is really hard to
Then tilt the scope up
When it is this low, I
want the angles to work out such I can keep my little trapdoor shut and the
image will be above that and the door .will not get in the way of the image
I taped two State Fair
yardsticks together. The six inch marker will be centered on the axis and,
from that, the end of the yardsticks will be four feet from that center.
I start by lining up the
six inch marker on the center of the Declination axis.
Then I note the end of
the OTA falls on 33 1/4". Gotsta to remember this.
We then tape the yardsticks
to the bottom of the scope so the 33 1/4" mark is at the end of the tube.
Later, I flipped the sticks
on edge, not flat, to the scope. This yieleded a more accurate measure to
the end of the yardsticks.
We need to measure how
far the trapdoor comes up from the base of the dome
Now, from this, we can
calculate the wall height. Right?
Note: This is an earlier
model dome and the newer ones may have a different dimension.
We make sure the tripod
is level .
The height to the base
of the wedge is 29 1/2". I used 30" for all my calcs.
The measure to the top
of the trapdoor will be 63". I rounded that to 64" for good measure.
Now, the math.
The top of the stick is
the bottom of the OTA.
We need to make the Dome
trapdoor 64" from the base of the deck for the fifteen degree test.
Knowing the height of
the trapdoor is 20", this places the top of the Rings at 44".
64" minus 20"
The Ring Assembly is 5
3/8" tall. I rounded this to 5".
The top of the wall then,
will be 39".
44" minus 5"
I am putting a one inch
thick cedar deck lumber on the base of the wall. So, the wall has to be 38"
64" minus the Trapdoor
of 20", minus the ring height of 5", minus the 1" weatherproof
deck lumber equals 38" for the wall panels.
Now, we are finally ready
to chop some wood.