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Making an affordable £30 star tracker


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If you want to take images of the night sky, you need a long duration exposure to capture the faint starlight.  The stars, however, are constantly moving across the sky. While it is perfectly possible to take short exposures that avoid trailing, it soon becomes apparent that the camera needs to track the stars. 

I wanted a tracker that would follow the stars to allow me to capture the beauty of the summer milky way or follow another bright comet. While it is easy to use the credit card and buy one of the commercial star trackers (available at a variety of prices and capabilities), I wanted something more affordable and set about making my own tracker from scrap plywood, B&Q hinges and a length of steel rod and odds and ends from the spares bin.  Total cost was £30 (£50 if I include the stuff I already had).

This design is a barndoor tracker (as it works like a barn door!) sometimes a Haig mount after its inventor and sometimes a Scotch mount as Haig was Scottish!  It is simplicity personified.  I found the challenging bits to be bending a curved rod around a template and secondly butchering the motor mounting so that the gears mesh together effectively. The rest is so simple. Total time was a few evenings – perhaps a bit longer as I stopped to photograph and record the build process.

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Having enjoyed tracking the moon between showers earlier this week with a guestimated polar alignment, I am keeping my fingers crossed for clear skies later this week to test it under the stars.

As always if you have any questions or comments then let me know.

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I hope the skies were better with you on Wednesday night!  It was very hazy here.  The thin cloud was also back-illuminated by the gibbous moon making all but the brightest stars invisible.  Certainly not good enough for observing but good enough for a play.

Polaris was only in the finder scope by dead reckoning, once I had dialled in 51deg elevation and magnetic north using my phone.   

60s of Lyra using a 50mm f2.8 showed the clear benefit of tracking. 

60S: tracker turned off:

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60s with tracking:

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I just need to check the mount is rotating about the hinge at the sidereal rate as there is still some trailing, particularly at 1 minute (albeit much less). 

With that in mind, the following morning, I blue tacked my protractor from my flying kit to the tracker, made a pot of tea and fine tuned the motor so it was tracking at 1deg every 4 minutes or 5deg in 20 minutes ready for the next clear night. 

I am now getting a smidge under 15deg in 1 hour so ~0.5deg error which is 3%.  I am hoping, it is good enough for government work - assuming government work is 1-2 minute exposures at a relatively wide angle. 

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I will also check the finder scope is truly aligned with the hinge in daylight - once the rain has stopped that is.

 

 

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Hussah, a clear night. Time to test the homemade barn door tracker. Not too shabby but we are getting there - subject to weather and dark skies.

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Edited by MarkRadice
typo
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