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Rough in AZ/ALT with only the Tri-Pier Legs

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#1 string

string

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Posted 20 December 2020 - 02:25 AM

I've picked my spot. I'm installing POD, purchased used with a 2 x 6, deck block substructure that is topped with 3/4" marine plywood. that's perfect for my semi-permanent needs. It will be housing a CEM70g on a Tri-Pier. My goal is to leave no sign of the installation should I need to move it or remove it.

 

To center the pier the back leg(s) come down directly on a rear floor joist. I must run north between legs so that only one leg comes down to the south and therefore I only have to make one one cut to one joist. I can't just turn the Pier top as I want Zero to be centered between legs for my heavy payload.

 

I must determine exact the position that the TP legs will come through the plywood so that the alt/az is basically good before doing a PA with the mount. I'm not expecting perfection but I want it to be close... by moving the legs while keeping the pier in the center and the mount's zero position points as close to Polaris as possible.

 

I started with a compass calculating the magnetic deviation of my location but never could get comfortable with the math. My head hurt.

 

I decided I will use my 50mm guidescope w/eyepiece and also a laser to help me point right to Polaris with only the Zeroed mount on the next clear night... Adjusting alt.az only with the legs. Attitude does not matter at this point but I can rough that in on the mount.  I'll mark the ground where the legs come down so that I know where to put the 3 concrete risers and also correctly cut the holes as small as possible in the plywood floor.

 

In the photo you can see a board in the background that roughly points to Polaris. Thats how much I need to turn the Tri-Pier but I want to do a more  accurate job than this. I know I can fix this with a PA but I don't want to be looking at an az/alt setting way off to one side for months/years. I'll never be able to easily move the Tri-Pier after the POD foundation is built. and the POD itself installed.

 

I know this sort of a unique semi-permanent case. Does anyone have a better idea for what I'm trying to do?

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  • TRI-Pier_Joists.jpg


#2 string

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Posted 21 December 2020 - 07:48 AM

I eyeballed the altitude with the mount using the pen laser. Then I dialed in the azimuth with only the Tri-Pier Legs using my guidescope and a 6mm eyepiece. The mount was in zero position and perfectly lined up to Polaris. I'm ready to place the risers now. Sometimes the simplest of solutions is the best one.

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  • TPADJ.jpg


#3 string

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Posted 23 December 2020 - 01:51 AM

First Light... of the floor anyway. After setting the risers, I installed the floor and tonight I did a Polar Alignment using only the Tri-Pier Legs. The mount was at zero with no power. I used a laser plumb line to center the pier in the circle and rotated the legs with the pen laser. Then I could dial in Polaris with a 3.5mm EP. Marked the legs on the floor. I'll have to do the math... taking out for the 4" down that the legs will rest beneath the floor. The clouds parted and it was a beauty of a night. I remembered why I'm doing this.

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  • Floor_first _light.jpg

Edited by string, 23 December 2020 - 01:59 AM.

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#4 string

string

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Posted 31 May 2021 - 10:25 PM

My semi-permanent installation is now paying off. I have decided to move the POD to the east side of the yard before nebula season for a better southern view. It will be very easy to do. So far I've only had a few clear nights for months. I finally got a chance to run iPolar since I swapped the 9.25 for the RASA Twins and bumped around a lot getting set up. I expected a total mess. The AZ was still perfect and the ALT had moved just a bit. In 60 seconds I was polar aligned again. I post this for anyone else who might need a temporary solution in the future. I would recommend this in certain situations.

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  • polarNoTouch.jpg



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