Polar Mount Inclination Calculator

Calculator Form

Site Latitude

Use decimal degrees. Signed values are accepted.

Hemisphere

Earth To Orbit Radius Ratio

Default 0.15127 suits geostationary calculations.

Offset Dish Angle

Use 0 for prime focus dishes.

Mount Scale Type

Decimal Places

Optional Job Note

Formula Used

The calculator uses latitude as the main polar mount reference.

Let φ be the absolute site latitude.
Polar axis elevation above horizon = φ.
Inclination from vertical = 90 − φ.
Let k be Earth radius divided by geostationary orbit radius.
Declination offset = atan((k × sin φ) ÷ (1 − k × cos φ)).
Central dish elevation = 90 − φ − declination offset.
Offset dish face reading = central dish elevation − offset dish angle.

These values are starting settings. Final peaking still needs signal testing.

How To Use This Calculator

Enter your site latitude in decimal degrees.
Choose the correct hemisphere for the aiming direction.
Keep the default orbit ratio unless your guide states another value.
Enter your dish offset angle, or enter zero for prime focus.
Select the scale type printed on your mount bracket.
Press the calculate button.
Read the result above the form.
Download CSV or PDF for your alignment record.

Example Data Table

Latitude	Polar Axis Elevation	Inclination From Vertical	Declination Offset	Central Dish Elevation
15°	15.00°	75.00°	2.63°	72.37°
25°	25.00°	65.00°	4.24°	60.76°
35°	35.00°	55.00°	5.66°	49.34°
45°	45.00°	45.00°	6.83°	38.17°
55°	55.00°	35.00°	7.73°	27.27°

Polar Mount Inclination Guide

A polar mount lets a motorized dish follow the geostationary belt with one main rotation. The mount axis must point parallel to Earth’s axis. This is why latitude drives the first setting. In many manuals, the polar axis elevation equals the absolute site latitude. Some brackets show the complementary inclination instead. That value is ninety degrees minus latitude.

Why Declination Matters

The dish does not point exactly along the polar axis. It must lean down by a small declination offset, because satellites sit above the equator, not on an infinite circle. The offset grows with latitude. A small error can still move the signal peak, especially with narrow beam dishes. This calculator includes the geostationary ratio, so the estimate stays useful for different assumptions.

Reading the Results

Use the axis elevation when the mount scale reads above the horizon. Use the inclination from vertical when the scale begins at the upright position. The central dish elevation shows the boresight for a prime focus style dish at the top of the arc. If an offset dish angle is entered, the tool also estimates the apparent face reading. Use that value only as a starting point.

Practical Alignment Tips

Level the pole before setting any angle. Tighten bolts only enough to hold movement while you test signal. Aim the axis toward true south in the northern hemisphere, or true north in the southern hemisphere. Magnetic compass readings need local variation correction. Peak the center satellite first. Then check satellites on both sides of the arc. If both ends miss in the same direction, adjust the whole mount. If one side improves while the other worsens, recheck pole level and declination.

When to Recalculate

Recalculate after moving the antenna, changing the pole, or replacing a motor bracket. Use decimal latitude from a map app or GPS receiver. Rounded latitude is usually fine for a quick setup, but precise values help during final peaking. Record every setting before adjustments. This makes it easier to return to a known position when wind, loose hardware, or scale marks cause confusion. The exported table can become a small alignment log for future maintenance. Save notes beside each exported run for faster troubleshooting later.

FAQs

What is polar mount inclination?

It is the angle used to align a polar dish mount with Earth’s rotational axis. Many mounts show it as a tilt from vertical, while others show polar axis elevation above the horizon.

Is inclination the same as latitude?

It depends on the bracket scale. Polar axis elevation usually equals site latitude. Inclination from vertical is normally ninety degrees minus the absolute latitude.

Why does the calculator show declination offset?

The dish beam must be lowered slightly from the polar axis. This adjustment helps the dish follow the geostationary satellite arc more accurately across the sky.

Should I use true south or magnetic south?

Use true south in the northern hemisphere. Use true north in the southern hemisphere. Compass readings may need magnetic variation correction before final alignment.

What does the orbit ratio mean?

It represents Earth radius divided by geostationary orbit radius. The default value is suitable for common polar mount declination calculations.

Can I use this for an offset dish?

Yes. Enter the dish offset angle. The calculator estimates the apparent dish face reading, but final signal peaking is still required.

Why is my mount scale different?

Some mounts label elevation above horizon. Others label inclination from vertical. Select the scale type that matches your hardware manual or bracket markings.

Are these final installation values?

No. They are strong starting values. Pole level, bracket accuracy, dish shape, local obstruction, and signal meter readings still affect the final setting.