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[michelb]

I'm in the proces of choosing a set of steppers to use on my Vixen New Polaris GoTo project.

I bet the save choice is this one: http://www.omc-stepperonline.com/nema-17-bipolar-stepper-12v-04a-40ncm567ozin-17hs150404s-p-14.html
For me it is a good combination of torque en weight. But the thing is that when I buy two steppers the shipping costs more than double the price, so I´ve been looking at ebay as well.

On ebay I see lots of nema 17 stappers, but most steppers with lot of torque use more than the 1,25A the DRV8825 can handle whitout heatsink.
Alternative one: http://www.ebay.nl/itm/221420132370
Alternative two: http://www.ebay.nl/itm/281633378754

The first is, for two stepper only slightly cheaper that a set from omc-stepperonline, but it's torque is also much less.
The second is much cheaper, has enough torque, but it is rated at 4,2V and the current per phase is 1,2A. When I use the stepper at 12V, can the AstroEQ controller handle the required amps and will the torque remain enough?

Until now I've been looking for a stepper with at least 360Nm torque. I imaginge that will be enough for my Vixen NP, probably more than enough, but  I'm uncertain until how far I can drop the torque before it is to low.

Who can help me choose the right stepper?

[TCWORLD]

Hi,

For an electrical standpoint the second one would be perfectly acceptable. In fact the lower the voltage rating the better (as long as the rated current is not to high). 1.2A/phase shouldn't be an issue.
The only peculiarity about that motor is the shaft comes out the opposite side from the mounting holes, but given that you'll be making the brackets anyway this shouldn't be an issue.

Regards,
Tom.