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Aligning the DEC axis to the RA axis

This portion of the procedure will assure that the DEC axis is orthogonal or perpendicular to the RA axis. Adjustments are made to the elevation of the fork arms to achieve perpendicularity. You will draw a set of perpendicular lines on a wall. Call this the target. Then using the laser you will sweep the beam across the horizontal line of the target by rotating the scope around its RA axis, and the vertical line or the target by rotating the scope around the DEC axis. If the RA axis and the DEC axis are not perpendicular the beam will stray from the vertical target line. When sweeping the beam along the line in this procedure try to be as precise as possible. Draw a thin line, and when lining up the beam dot on the line actually line up the edge of the beam dot on the line. That way it is easier to determine when the beam strays from the line.

Step 1. Place the scope tripod so that when the scope is mounted in the ALT-AZ arrangement the front (corrector plate end) is about one foot from a flat wall. Try to find a spot on the wall away from a drywall joint to assure the surface is flat. Level the scope tripod. This does not have to be exact. A rough leveling will do fine. Mount the scope in ALT-AZ arrangement.

Step 2. Wrap a piece of tape around the laser pen ON button to hold the button down causing the laser to be on continuously. Then tape the laser pen to the top of the scope. If you have a mount rail or camera mount tape the pen to it instead of directly to the OTA. This will raise the beam above obstructions caused by the corrector plate cover and rim.


Fig 3

Figure 3 - Laser pen mounted on scope


Step 3. Tape 4 sheets of 8.5" X 11" paper together lengthwise to produce a single sheet approximately 8.5" X 44." Use a carpenter's square or straight edge to draw a straight line from one end to the other lengthwise along the center of the sheet. You will need two of these large sheets of paper.

  Fig 4

Figure 4 - Draw a straight line on paper

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