Need help from the hardware Gurus

[tsk1979]

Hello fellas
As many of you know, I love making Time lapses.
If you look at youtube, you will see many time lapses showing actual panning(as opposed to software panning(fake panning effect)).
Now, you get devices like Radian and Astro which are programmable and all.
However the prices usually are about 200$+ going to 400$ for an astro tracker.

So I decided why not try to make something on my own.
I need to make a device with a 1/4"" screw for mounting a ball head or something. The screw will be connected to a slow rotating motor.

Now how slow.
I would live a device where I can have

1 full rotation takes 1 hour
1 full rotation takes 2 hour
1 full rotation takes 3 hours
1 full rotation takes 5 hours
1 full rotation takes 10 hours

So 5 settings possible

The rotation has to be smooth. No jerkes and all. So maybe 800 steps/rotation is needed.

Where can I buy such motor which can be programmed to achieve this. I think I will need a 6 speed gearbox to connect to this motor to achieve this.

I am trying to keep the cost below 100$ or whereabouts. Also a good idea would be to have it run via 3.7V lithium battery.

Since I am India, buying parts from a single vendor is desired as I will save on shipping.

Any ideas fells?

 

[pschlosser]

Hmm, interesting challenge.

It's too bad you cannot use a wall clock, and it's clock motor to rotate the camera. It's slow and smooth enough. But the speed doesn't vary, so that won't suit all your needs.

Gear reduction is your best bet. An electric motor won't likely have small enough resolution to rotate 360 degrees in 10 hours. or even one hour. When you factor in several gears, to give you the gear reduction you need, an off the shelf solution designed for such purposes may be what you're looking for.

Maybe researching hobbyist astronomers and telescope rotation. Surely there have been some economical solutions proposed on those areas of study.

 

[123splat]

Look up (Google) "Barn Door Mount"

 

[pschlosser]

Well done, Splat. The Haig mount is a great start. I seem to recall there was some kind of error introduced because the screw drive is straight, instead of curved. But for tsk's needs, this may be just the ticket.

+1

 

[123splat]

Ja, small linear error from using straight shaft. There have been several attempts to avoid the issue by using things like lobes on the drive, but by far the best solution is to bend the shaft in a slight arch. works extreemly well. No need to correct after 10 -15 minutes run time.
Bigger problem is to find a decent, but fairly inexpensive, DSLR with a longer bulb set than 3-5 minutes (Nikon... ) Canons seem to have a step up for astrophotography.

 

[tsk1979]

barn door mount seems to be a great idea!
Second is 400:1 gear reduction.
I will explore both angles. Accuracy does not matter because I am not doing deep sky astro. Just doing panning time lapse, so want something rotating real real slow!