There are various methods for aligning the orientation of a telescope mount with the pole, but one of the most popular is drift alignment. It’s often referred to as the ‘gold standard’ of polar alignment methods and has a reputation for being the most accurate. The picture left shows how a failure to polar align correctly will cause your stars to trail in your images.
What exactly is Drift Alignment?
Declination drift occurs when the polar axis of the telescope mount is not aligned with the true pole. A star follows a particular path across the sky as the earth rotates, but if the star is being tracked by a telescope whose mount is not aligned with the earth’s rotational axis, then the star appears to drift in the north/south direction in the telescope’s field of view. We can take advantage of this to align the telescope’s polar axis. All we need to do is monitor the drift of the star and adjust the azimuth and elevation of the mount’s polar axis until the drift is very small.
Software tools you can use
Modern software tools remove the complexity of drift alignment methods for us and make it much easier than a manual approach (which you can still try if you are a purist!) When you can’t see Polaris (southern hemisphere as an example) some of these are extremely useful . Here are some examples with links to the differing ways to do this.
PHD2 Guiding Software
PHD2 (or “Press Here Dummy”) is the goto open source guiding software many amateur astro photographers use – its a fantastic tool and contained within it is their Drift alignment tool.
SharpCap (Pro version only)
SharpCap takes two pictures near the pole and analyzes them to judge the accuracy of your Polar Alignment. SharpCap uses plate solving to scan the images and then tells you how much you need to move your mount to increase the accuracy of your Polar Alignment.
This is one of my favourtie tools for ease of use and accuracy but requires you use ASCOM as does not work with INDI. There is a good tutorial here from Trevor at Astrobackyard so I will not rejurgitate it… and Ray has done a YouTube video tutorial.
Ekos Polar Align Tool
When I am using INDI on my RPi, and do not have IPolar available, as on my older AVX mount, I often use the Ekos polar alignment tool, a provisio is though that your field of view is more than 1 degree otherwise it cannot successfully plate solve during the process. I also ensure the viewing wondow is un-docked and full size as this really helps.
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