How should a laser pointer be mounted for polar alignment on a barn door tracker?
Asked 2/2/2019
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I’m building a simple barn door tracker for basic astrophotography and I’m unsure how to mount a laser pointer for polar alignment. Does the laser need to be attached to a specific plank or directly above the hinge, and does the distance from the hinge matter? I’m mainly trying to understand the alignment requirement when aiming the tracker toward Polaris.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
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It doesn't matter where the laser pointer is mounted. The important thing is it should be perfectly parallel to the hinge axis. That is, the hinge axis (hinge pins) "point" to the polar alignment position, which in the northern hemisphere is very close to Polaris. In the southern hemisphere, it's not nearly as easy, but it's a few degrees off from the Southern Cross.
As long as your laser pointer is exactly parallel to the hinge pins, it doesn't matter how far away from the hinge the pointer is. For instance, assume you point to Polaris. That star, while it appears to be a tiny point from our perspective, in fact is many, many, many times larger than the separation distance between the hinge pin and the laser pointer. It's many many times larger than the Earth diameter, for that matter.
Originally by user11924. Source · Licensed CC BY-SA 4.0
user11924
7y ago
0
Generated from our catalog & community — verify before relying on it.
The exact mounting position doesn’t matter. What matters is that the laser beam is perfectly parallel to the hinge axis (the line through the hinge pins), because that hinge axis is what must point at the celestial pole.
So:
- Mount the laser anywhere convenient on the tracker.
- It does not need to sit directly above the hinge.
- Its distance from the hinge also does not matter.
The key is careful adjustment so the beam is parallel to the hinge pins. Once that’s true, aim the hinge axis toward Polaris in the northern hemisphere for polar alignment. For astrophotography, alignment accuracy matters more than the exact bracket location.
In short: choose a mount that lets you fine-tune the laser’s direction, and focus on making it parallel to the hinge axis rather than placing it at any exact spot on the wood.
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AI7y ago
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