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RA Motor drive?


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Hi all,

I've been looking at a few motor drives and am wondering, unless I went for a full goto upgrade kit, is there any point in going for a dual axis drive ? I know that a RA axis drive is more or less essential for astro photography but cant see the need for dual axis or am I wrong?

Also are there any alternatives for my Skywatcher EQ3-2 mount other than Skywatchers own RA drive? ANd is the single axis drive any good?

Kev.

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I would imagine that an auto guider would need dual axis drives in order to guide accurately for long exposures.

Although being a visual only guy I am guessing, no doubt someone will tell you if I'm talking piffle.:)

You may be better off posting in the imaging section.

Regards Steve

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Hi,

This is th ewrit eup for the dual axis motors " Provides multi-speed quartz-controlled electronic motor tracking of the R.A. & DEC. axis. "

So will this track smoothly for AP

Whats the difference between guiding and tracking?

I can only assume guiding finds the objects and tracking follows it.

Kev

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Tracking is simply where the mount is motorised in RA to follow the object as it moves across the sky. Handy for visual work and essential for astrophotography, but if you want to get into really long exposures, then tracking alone is not generally accurate enough, and this is where guiding comes in.

The tracking system in many mounts is not precise and there are periodic errors in the gears. What this means is that you will notice star trails appearing relatively quickly, within a couple of minutes or even less. Guiding involves use of a guide camera, which is attached either to the main scope or to a second 'guide scope'. The guide camera is focused on a single star (the guide star), and when that star moves more than a pre-defined distance (normally a couple of pixels) away from the crosshair, then the camera relays the information to the mount to correct the error so that the guide star remains centred. This way the scope stays locked on target allowing much longer exposures. Obviously this requires a computerised mount with the necessary ports.

Going back to your original question, I have a dual axis motor and, although not necessary for visual work, it is handy being able to move in all directions with the one handset; you can hold it and press all the buttons while looking through the eyepiece. With RA drive alone, you could use the handset to move in RA, but would have to use the knobs to make adjustments in Dec, so just that bit more fiddly.

Hope that helps.

Rachel

Edited by The Bat
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Thanks,

Yes that does help and makes everything a lot clearer, Money dictates that a guide camera set up is out for quite a bit so I'll look into getting dual axis motors.

Have you got to fit Skywatcher to Skywatcher mounts or are there better different makes available for similar prices?

Kev

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On the EQ3-2, dual axis motors gain you nothing in terms of tracking. The DEC motor is only for fine tuning the object in the eyepiece, and does nothing while tracking. It's handy for centering objects in the eypeiece, but you already have the slow mo control knob for that, so it's no big deal.

Remember, the motors for the EQ3 are dumb.. they have no guide ports and accept no inputs from anything... they just track in sidereal time. Once polar aligned, you have no need to track in Dec because objects don't move in teh dec axis.. you need RA only.

save the £12.

Edited by pook
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