Motor info please.

For those who need help choosing a setup or want further advice on how to improve their own setup
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plord

Motor info please.

Post by plord » Sun Nov 25, 2012 7:18 pm

Does anyone know the RPM speed of the RA motor for an EQ1 mount?
Searched online but no luck.
Peter.

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rwilkinson
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Re: Motor info please.

Post by rwilkinson » Sun Nov 25, 2012 8:17 pm

According to this thread:
http://www.cloudynights.com/ubbthreads/ ... in/5071162
the EQ1's crown-wheel has either 96 or 100 teeth, so you'd need the motor to drive the worm-gear at around 0.068 rpm.

I used to have an EQ1 with a variable-speed motor, a bit like this one:
http://www.ebay.co.uk/itm/Single-Axis-D ... 0535296358

plord

Re: Motor info please.

Post by plord » Mon Nov 26, 2012 12:16 pm

Thanks for that Ross
Hmmm... less than 1rpm? I have a stepper motor + gearbox which might do the trick,
I have had the EQ1 for some time and was going to throw it out until my astro interest was re awakened after joining BAS!
I am in the process of stripping down the head and getting rid of the sticky goo which seems to be everywhere including the gears, and replacing it with Lithium based lube.
I hope to use the finished head for imaging with DSLR / webcam, rather than observation.
Regards
Peter

PS if I used extra gears and increased the motor speed, would this increase accuracy even on such a low end head or is it a waste of time?

Forgot to add, I have counted the teeth on the main gear and I made it 100 so that seems to fit.

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Re: Motor info please.

Post by rwilkinson » Mon Nov 26, 2012 4:29 pm

Yes Peter, a stepper-motor is ideal for this application.

If you remember that your mount needs to turn at the same speed as the Earth - once every 23 hours 56 mins (= 1436 mins) and your crown-wheel has 100 teeth, then the worm-gear needs to rotate 100 times per day, i.e. evey 14.36 mins - hence 0.0696 RPM.
If there are any other gears in the drive-train then their ratio needs to be included in the same way, but I'd have thought the fewer gears the better - they are only going to add more back-lash.

I'm not sure that it's worth spending a lot of effort on system based on a cheap 100-tooth gear, but if you only want to do wide-angle images with a DSLR and lens then it may be good enough. For better results you'd need bigger precision gears (a crown-wheel with 300 - 400 teeth works well).
And the other thing you're lacking is a quick method of polar alignment: there's no provision for a polar-scope on the EQ1.

But why not arrange to borrow the BAS Astro-Mount:
http://www.boltonastro.co.uk/forums/vie ... f=17&t=156
and see how you get on with that first?

plord

Re: Motor info please.

Post by plord » Mon Nov 26, 2012 10:42 pm

Thats a very good idea Ross, I'll see how things work out when I put my EQ1 back together.
Thanks for the help and advice!
Peter

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