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Barn door tracker


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Just been modding my barn door tracker that I made a couple of years back and thought I might

post a bit about it.

Its based on the designs found here


and was made using heavy ply so that it would carry most of what

I wanted it to.

The stepper motor came from a scrap printer and the driver board was

from this UK electronics kits company.


This is a picture of the beast sat on my 4"*4" wooden pier.

The lens in an MDF box on top the mount is a 40mm lens that I stick in front

of my webcam when I'm too lazy to get the scopes out.


Mostly though, the tracker is used with my Nikon 5400 digital camera

for widefield shots. This camera can image up to 10 minute exposures

so you can see the potential.

The board has had a paint job and a few tweaks to the motor mount

so with luck I should get some good shots of the summer triangle area.

Just to show what the tracker/Nikon combination can do, here is an image

I took of comet Machholz last year


Will post some images from it as I get them :)

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To show why the tracker was "over built".

Here is a picture of it carrying a home made 80mm F5 refractor made from cheap

bits from Surplus Shed with the Nikon 5400 bodged on the back taking afocal images of sunspots.

Quite a weight and it all looks a tad ugly but it works :)


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How do you drive the tracker


The stepper motor attached to the bottom board drives the top board (open and shut) via a 6mm threaded rod.

Motor speed is governed by the frequency of a quartz crystal oscillator.

Whole thing runs on 12 volts so I could take it to a dark site on a tripod

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A close up of the tracker showing the motor hanging on a pivoting wood plate.

The 6mm drive shaft goes through a threaded pivoting rod in the top board.

Also on this picture is another mod I made early on.

Its the red wheel on the side of the top board which runs on a wooden plate screwed to

the bottom board.

This helps to alleviate any twisting action on the tracker hinge due to the heavy(ish)

weights it sometimes carries.


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Do you have trouble with polar alignment and speed adjustment


Polar alignment is done using a 10mm sighting tube glued on the top board parallel to the tracker hinge

to find Polaris. Then I did a drift align, adjusting the wedge angle and the tracker azimuth to suit.

Beauty of it being on the pier is that now I can put the tracker on the pier aligned to marks put there

after set up. Only takes a couple of minutes to get up and ready.

Speed wise, the crystal oscillator frequency can be "pulled" slightly to match siderial rate.

I found if the calculations were correct and the placing of the drive shaft relative to the hinge

was as close as you can get it then speed accuracy is less of a problem than say polar alignment.

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