My Barn Door Tracker

[Sivakis]

Can't wait to test it out on a clear night!

Took some photos, thought to share with you, esp. for those who still on the fence on this one.

1. 2 wooden boards, connected by hinge:


2. This was the tough bit for me. The tripod mount was on a 1/4 screw and it was simply too short to mount on the wood properly.


3. Since I couldn't find a 1/4 T-nut anywhere in Singapore (or maybe I don't know where to find....), I was relieved that the mounting plate could be dismantled:


4. Screw removed


5. Longer 1/4 screw replacing the short one


6. Did all the rest of the standard drilling, connecting and voila!


7. The driving bolt with T-nut
This is a 6mm bolt (which I could find the T-nut for). Most schematics out there ask for a 1/4 bolt at distance of 29cm from the hinge. Because I'm using 6mm instead, I had to change the distance to 22.78cm (thanks orly for this!)


8. In trying to find an easier way to turn the driver-bolt, chanced upon an old credit-card that's expired. Perfect!


9. Everything up!



The driver-bolt is good for only 18 turns. The good thing is that I can always change it for a longer bolt in the future if I need to, with no change to the other stuff.

Have fun!


For more information on barn door trackers, you can head to:
http://www.nightskypix.com/equip/ScotchMount.htm

http://starnamer.blogspot.com/2005/09/m ... -barn.html

http://stargazerslounge.com/diy-astrono ... acker.html

[rcj]

very nice! and thanks for sharing the detailed pics... had tried to do this tracker albeit with a motor many years back. eta carinae on film then! simple yet rewarding. if u still need nuts or bolts, screws let me know!

[timatworksg]

Nicely done Sivakis! At least you got yours done and settled...lol! I'm still contemplating on a new design (fussy lah). Do some test to get the movements right! It's all practice now. Best of Luck!!

@Remus
Bro...looks like you got too much junk...HAHA! Time to raid your house!

[orly_andico]

18 turns should be plenty.. that's 18 minutes. with sky conditions in Singapore, you'll be limited to 1-2 minutes tops anyway.

[Clifford60]

For the driving bolt, is there a different in the thread pitch between the 6mm bolt and the 1/4" bolt? I guess the pitch is more important that the diameter (size).

Also, you invert the driving bolt as compare to the design by Andy Weeks, the angle change per bolt turn will be different.

Anyway, may be the change you have done will offset for the differences.

Last but not least, good job and good effort

[Sivakis]

Yes, there's a thread pitch difference between the two and yeah, it's more the pitch than the diameter.

I'm not sure if there's a difference between a push or lift bolt-action. There shouldn't be.

Of course, ideally, the bolt should be curved in the same as the hinge movement to minimise the bolt-slip causing vibrations to the camera but the movement is very minute.

Anyway, yet to test it, so it's all still to play for

And thanks for the encouraging replies! Let's wait for some clear skies ;)

[timatworksg]

Sivakis,...if you find the bolt pushing a little too easy, you could add some tension by adding eye hooks at the sides of the top and bottom board and loop some rubber bands to provide some pull down spring. Some tension will give the push some tension allowing for a smoother controlled movement.

[Sivakis]

It's actually very smooth atm. There's only a little play on the round-nut sitting on the bottom plank all the way through to Turn 18 and the wood's smooth.

Stupid moon is out tonight so nothing is showing though...

[Sivakis]

Revisiting an old friend....

I'm pretty bad at electronics so bear with me if what I say doesn't make sense.

To motorise my barndoor, the most basic components I'll need would be:
1. a motor (duh? lol)
2. wires
3. a way to fasten the driving bolt to the motor
4. batteries

That's about as basic as it gets, i think.

So am I correct to assume that if I get a 12V 10RPM dc motor and I want to scale it down to 1RPM, I can:
a. Use 2x 1.5V batteries to slow it down to 2.5RPM (12V/3V = 4. 10RPM/4 = 2.5RPM?)
b. Reduce the RPM further by use of a second gear that's 2.5x the diameter of the gear fastened on the motor to turn the driving bolt
c. Maybe an on-off switch to control the start/stop.

Does the above actually work? Or am I spouting nonsense?

[orly_andico]

Sadly, scaling down the voltage won't provide a linear reduction in speed. So that won't work.

Your best option is to fine a real 1 RPM motor (even then it won't be terribly accurate) or use a stepper motor. If you're handy with electronics like Arduino it should be fairly straightforward to make a stepper motor controller.