PoleMaster—electronic polar alignment

The problem with traditional polar alignment

The polar scope method works, but it has real limitations. It requires a view through the mount's polar scope, which can be obstructed by the telescope or camera. The illuminated reticle needs to be calibrated to the mount. And achieving precision better than a few arcminutes by eye is genuinely difficult.

Drift alignment gives better accuracy but takes considerably longer, rotating the mount, observing star drift, and iterating. For regular observers setting up at different locations, or for remote observatories where the initial alignment is done via a remotely-operated camera, this is impractical.

How PoleMaster works

PoleMaster uses a high-sensitivity CMOS camera with a wide field of view (approximately 11° × 8°). The camera mounts to the polar axis of the equatorial mount via a dedicated adapter. A dedicated software application on a connected PC guides the process:

1. The software identifies the pole area in the camera image and finds reference stars
2. You rotate the mount through a specified arc so the software can locate the true rotation axis
3. The software shows you exactly how to move the mount's altitude and azimuth adjustments to bring the pole to the correct position
4. The process iterates to refine the result, converging on sub-30 arcsecond alignment

Specifications

Mount compatibility

PoleMaster needs a specific adapter for each mount, since the hole diameter at the RA axis—where the optical polar scope normally looks through—varies from one mount to another. Dedicated adapters cover the mount models most commonly used by amateurs: Sky-Watcher, Orion, Celestron, Takahashi, Losmandy, Vixen, and even Astro-Physics mounts such as the AP900. The camera body itself is the same for every mount; only the adapter ring differs.

Field test: GoTo accuracy

To see whether PoleMaster actually beats a careful visual polar alignment, a reviewer for Revista Astronomía (issue 215, May 2017) ran both methods back to back on the same EQ6 mount, on the same night, with the tripod levelled the same way each time.

With PoleMaster, a three-star GoTo alignment was run using an ED80 refractor with a 35mm Eudiascopic eyepiece (about 2.66° of field), slewing to nine stars in turn. Most landed practically centred in the field; the worst GoTo miss measured was about 11 arcminutes 13 arcseconds.

Repeating the same GoTo sequence after aligning with the mount's classic optical polar scope instead, several targets showed clearly larger and more frequent deviations. The worst miss measured this time was about 20 arcminutes 13 arcseconds—nearly double the worst-case error seen with PoleMaster.

Field test: declination drift

Polar alignment accuracy matters most for autoguiding, since a poorly aligned axis shows up as steady drift in declination. Using a 9mm illuminated reticle eyepiece with a 3x Barlow (200x) on the ED80, the reviewer centred Spica in the reticle and waited 30 minutes.

After the PoleMaster alignment, Spica had not moved from the centre of the reticle—no measurable declination drift, aside from the mount's own periodic error along RA. Repeating the test after an optical polar-scope alignment, the star had drifted by roughly 1 arcminute 12 arcseconds over the same 30 minutes.