ETX TECHNICAL TIPS
From: Kelvin Lee (LeeK@NMRIPO.NMRI.NNMC.NAVY.MIL)
Here's another homemade tripod design. The original Treepod v1 was the ETX attached to a 4 x 4 stuck into a Christmas tree stand - it was very stable but had too much flex (from the stand). The current version is (top to bottom):
1). The ETX (with essential Orion EZFinder) attached by all 3 center leg holes (with 1/4 x20 thumbscrews and wingnuts) to an -
2). Adjustable wedge made from 2 pieces of oak, 2 hinges and 2 lid supports (a permanent wedge would eliminate the flex introduced by the lid supports). I used the ETX baseplate as a template for drilling the center leg holes and the RA drive switch hole. To set the wedge at the correct angle for polar alignment, I set the declination of the ETX optical tube to my latitude. Then I tilt the whole wedge/ETX until the optical tube is pointing straight up (wedge angle = 90 degrees - latitude, to be really accurate you could use a spirit level place on the lens cover to be perfectly level) and lock the wedge in place. The wedge is attached by 2 1/4 x 20 bolts to a -
3). Top plate made out of oak. The top plate is attached by 5 screws to a -
4). 4 x 4 about 27" tall. This is sitting height for me, which is how I do all my observing. Although I don't agree with Ed Ting's ETX review, I wholeheartedly concur when he says that sitting adds at least 1 inch of aperture. The 4 x 4 is attached to -
5). 4 "L" shape cleats cut from 6 inch pieces of 2 x 4. The cleats are attached to the sides of the 4 X 4 with 3 screws each and attached to the base with 1/4 x 20 bolts.
6). Base. It's important this be heavy (especially with taller designs), a manhole cover would have been perfect. I ended up using a 2'x2'x1" piece of old maple countertop I had lying around. The bolts attaching the base to the cleats are recessed into the base, so heads of the bolts don't stick out from the bottom and completely scratch up the floor. I'm thinking of adding "feet" to the base so they poke into the ground.
The downsides to this design are the height is not adjustable, it's not exactly airline portable and you need a flat spot to set it on (although this probably exists in most backyards and anywhere you can drive). The upsides are this design is very stable and stiff with almost no torsional flex, it's compact (no trip hazard), attachment to the ETX is more secure and the weight is better centered than regular photo tripods. Best of all, it is cheap and really easy to make.
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