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I'm heading up to Scotland in April for a bit of a road trip and I'd like to give astrophotography a bit of a go. I'm like to try and get some deep sky photos (Andromeda etc) and have decided that rather committing to an expensive tracking mount, I'd just spend a small amount and give a barn door tracker a try.

I'm following this guide: https://barn-door-tracker.co.uk/

It nearly all makes sense but I'm a bit unsure about the polar alignment. I'm thinking I'll get a laser pointer as the above article suggests but I'm not really sure how to A) attach it to the wood (should it be attached to the top plank?) and B) does it matter how far from the bit of wood it sits? Does it have to be right on top of the hinge or does it not matter?

I was thinking of getting a mount like this: https://www.amazon.co.uk/EBTOOLS-Adjustable-Astronomical-Telescope-Aluminum-default/dp/B07MN54WCW/

Any advice would be super. Thank you!

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  • The idea is that alignment should align with the axis of the hinge, mounted very near the hinge. I'm wondering if it is moot point? That barn door tracker does look very nice. But you should be aware that the North Star (Polaris) coordinate location is approximately 3/4 degree from the true polar North (and which direction from Polaris varies with day of year), making something to aim this laser pointer at being in question.
    – WayneF
    Feb 3, 2019 at 2:09

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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.

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  • Thank you! I've read elsewhere that it helps to point the laser at something distant and then rotate the barn door a complete 180° and make sure the pointer is still pointing at the same to get it calibrated correctly. Is this correct?
    – Andy Furniss
    Feb 3, 2019 at 11:13
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    Yes, this is good advice. This makes sure your laser is mounted parallel to the hinge pin axis.
    – scottbb ♦
    Feb 3, 2019 at 12:43

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