How to Set Up an Equatorial Mount (Southern Hemisphere)

Goal: Align the mount's polar axis to the South Celestial Pole (SCP) for tracking stars with one axis. Near-enough alignment (±2°) is fine for visual observing.

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Prerequisites

• Equatorial mount + tripod
• Compass (or phone app with true south option)
• Spirit level (or phone app)
• Phone with declinometer (optional for precise altitude)
• Know your latitude (Google or GPS)

Australian Capital Latitudes (South)

City	Latitude
Melbourne	37.7°
Sydney	33.9°
Brisbane	27.5°
Adelaide	34.9°
Perth	32.0°
Canberra	35.3°
Darwin	12.5°

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Step 1: Choose & Prep Location

• Pick a spot with clear southern view (avoid trees).
• Tip: Use the same spot every time for faster future setups.

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Step 2: Orient Mount (Azimuth – Left/Right)

1. Face true south:

   • Stand several paces north of the tripod.
   • Use compass to find true south (not magnetic).
     • Melbourne: ~168° (180° – 12° declination).
     • Google local magnetic declination.

2. Align polar axis:

   • Look over compass toward tripod.
   • Rotate mount so polar axis points due south (directly above south horizon).
   • Get help if possible.

3. Level the mount:

   • Use spirit level on base.
   • Adjust tripod legs (don’t rotate mount).

Result: Polar axis points south, but altitude unknown.

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Step 3: Set Altitude (Up/Down)

Set polar axis angle = your latitude.

Option A: Use Mount’s Altitude Scale (Easiest)

• Adjust using scale on mount.
• Ensure mount is level first.

Option B: Use Phone Declinometer (More Accurate)

1. Calibrate phone on known level surface.
2. Hold phone against part parallel to polar axis.
3. Adjust until angle = your latitude.

How to Adjust

• Use two altitude bolts:
  • Loosen one, tighten the other.
  • Don’t force – back off one before tightening.

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Step 4: Attach Telescope

• Mount scope if not already attached.
• Balance with counterweights.

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You’re Aligned!

• At night: Center target (e.g., Pleiades).
• Track using only the polar axis (RA).
• Minor declination tweaks needed based on alignment accuracy.

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Quick Setup Next Time (Same Location)

• Leave altitude set.
• Keep leg lengths fixed (no re-leveling).
• Mark a south landmark (fence post, etc.).
• Use pavers for permanent spot.

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Pro Tips

• Some tripods have “N” leg → point south in Southern Hemisphere.
• Don’t align at night — do it before sunset.
• Near the pole? Axes behave weirdly — visualize RA position.
• Use Sigma Octantis (dim pole star) with binoculars for precision (advanced).

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Further Reading

• Astronomical Society of South Australia – Polar Alignment
• Next: Using catalog coordinates to find comets/planets.

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By Bill, Optics Central | For visual astronomy — precision to arcseconds is for astrophotography.

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Finding True South in Sydney

True south = geographic South Pole direction
Magnetic south = where compass points (Earth’s magnetic field)

In Sydney, magnetic declination ≈ 12.5° east
→ True south is 12.5° east of magnetic south

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Method 1: Using a Magnetic Compass

1. Find magnetic south
   → Compass needle points to 180°

2. Adjust for declination
   → Subtract 12.5° (since declination is east)
   → True south = 180° – 12.5° = 167.5°

3. Align your mount
   → Rotate so polar axis points to 167.5° on compass

Tip: Stand north of tripod, sight over compass toward mount.

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Method 2: Shadow Stick (Solar Noon) – Most Accurate

1. Find local solar noon
   → Use timeanddate.com or app
   → Example: ~1:00 PM AEDT (varies by date)

2. Set up stick
   → Vertical stick or plumb line on flat ground
   → Mark center base point

3. Mark shortest shadow
   → Watch shadow as noon approaches
   → At exact solar noon, mark tip of shadow

4. Draw the line
   → Line from base → shadow tip = true south
   → Opposite direction = true north

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Why the Difference?

True South	Magnetic South
Points to geographic South Pole	Points to Earth’s magnetic field
Fixed (geographic)	Varies by location & time
Needed for polar alignment	Compass default

Declination changes slowly — check current value at:
geomag.nrcan.gc.ca

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For equatorial mount setup: Use true south (167.5° in Sydney) to align polar axis.

Drift alignment

When you see arcing in a 30-second exposure with an equatorial mount, it means your polar axis is not perfectly aligned with the North/South Celestial Pole (NCP/SCP). The direction of the star trails in your image (specifically their drift in Declination, or North-South) can be used to determine exactly which way to adjust your mount's altitude and azimuth.

This fine-tuning process is often referred to as drift alignment, which can be done visually with an eyepiece reticle, or more precisely with a camera and guiding software.

Using Star Arcs to Fine-Tune Alignment (Drift Alignment Method)

The goal is to adjust your mount so that a star placed on the celestial equator does not drift north or south in your camera's field of view over several minutes.

Step 1: Set Up for Measurement

Target Star: Point your telescope at a moderately bright star located near the celestial equator (Declination around 0°) and close to the meridian (the North-South line passing directly overhead).

Camera View: With your camera connected, take 30-second exposures and examine the resulting star arcs or streaks. Ensure your mount's tracking is on.

Step 2: Correct Azimuth (East/West Error)

Observe the direction the star is drifting in Declination (up/North or down/South) across successive exposures:

If the star drifts South (in the Northern Hemisphere): Your polar axis is pointing too far East. Adjust the mount's azimuth (horizontal) control to move it slightly West.

If the star drifts North (in the Northern Hemisphere): Your polar axis is pointing too far West. Adjust the mount's azimuth control to move it slightly East.

(For Southern Hemisphere users, reverse the North/South and East/West directions for these steps).

Make small adjustments and repeat the exposure process, checking if the drift has lessened. Continue adjusting until there is no perceptible North-South drift for several minutes.

Step 3: Correct Altitude (Up/Down Error)

Once the meridian star's drift is corrected, move to a second star:

Target Star: Select a bright star about 20° to 30° above the Eastern horizon and still near the celestial equator (Declination around 0°).

Observe Drift: Watch the star's movement in Declination:

• If the star drifts South: The polar axis is pointing too low. Use the mount's altitude adjustment to raise the polar axis slightly.
• If the star drifts North: The polar axis is pointing too high. Use the mount's altitude adjustment to lower the polar axis slightly.

Step 4: Refine and Repeat

After adjusting the altitude, you might have slightly affected the azimuth alignment. For the most accurate results (especially for very long exposures), you may need to go back to the meridian star and repeat the azimuth correction process, then return to the eastern star for the altitude correction.

By iteratively making these small adjustments and verifying with 30-second test exposures, you can achieve very precise polar alignment. For even greater precision, many astrophotographers use dedicated guiding software like PHD2, which provides visual tools to monitor and guide the adjustments in real time.

To achieve sharper, untrailed stars in your astrophotography, a combination of precise setup and additional equipment/techniques is often required beyond basic alignment.

Key Setup Tips and Best Practices

• Balance the Mount Correctly: A well-balanced system reduces strain on the mount's motors and ensures smooth tracking.
• Rough Balance: Loosen the clutches (safely support the telescope) and adjust the counterweights along the shaft until the telescope remains in position when you let go.
• Slight East-Heavy Bias: Many astrophotographers intentionally balance their system slightly "east-heavy" in the Right Ascension (RA) axis. This ensures the gears are constantly pushing against gravity, which can improve tracking performance and reduce play (backlash) in the gears.
• Use a Sturdy, Level Tripod: The mount must be on a stable, level surface. Concrete is better than grass or sand. Keep the tripod legs as short as possible for maximum stability. Use a bubble level to ensure the tripod head is perfectly level before attaching the mount head.
• Minimize Cable Snags: Secure all cables (power, camera, guide camera, etc.) so they do not snag or pull on the mount during tracking. This can instantly ruin a long exposure image.
• Focus Precisely: Use your camera's Live View mode and zoom in on a bright star to achieve critical focus manually. The sharper your initial focus, the better the final image quality.
• Set Latitude Accurately: Before fine-tuning, set your mount's altitude setting to your local latitude. This gets you into the general ballpark for polar alignment and saves significant time.

Advanced Techniques and Equipment

Use a Polar Scope or Alignment Software: While manual drift alignment is highly effective, modern tools make the process faster and more accurate.

Polar Scope: Many mounts have a built-in polar scope that helps you position Polaris (or the SCP in the Southern Hemisphere) in the correct location relative to the celestial pole.

Software/Apps: Use smartphone apps like Polar Finder, or computer software like SharpCap or the ZWO ASIAIR app, which use plate solving (analyzing star patterns) to calculate and guide you to perfect alignment.

Implement Autoguiding: For exposures longer than 30 seconds, especially at longer focal lengths, autoguiding is highly recommended. This involves a second, smaller guide scope and camera that constantly monitor a star's position and send real-time corrections to your mount, dramatically improving tracking accuracy and allowing for very long exposures (e.g., several minutes).

Correct Periodic Error (PEC): High-end mounts allow you to train them to anticipate and correct for small, cyclical imperfections in their internal gears (known as periodic error). Autoguiding also helps smooth this out.

Stack Multiple Shorter Exposures: Instead of one extremely long exposure, take many 30-second exposures and stack them using software like DeepSkyStacker in post-processing. This method is more forgiving of minor tracking errors and helps reduce digital noise.