Single Axis vs. Dual Axis drives

We're looking at buying a telescope for our 13 year old son and are
looking at drives. What are the pros and cons of the single and dual
axis drives? What can you do with one that you can't with the other?
We're looking at the EQ-3M drives from Orion.

All thought are welcome.
Bill Lugg

wrote in message
oups.com...
We're looking at buying a telescope for our 13 year old son and are
looking at drives. What are the pros and cons of the single and dual
axis drives? What can you do with one that you can't with the other?
We're looking at the EQ-3M drives from Orion.

All thought are welcome.
Bill Lugg
Think first about what you are doing, when you drive a scope, and when you
'aim' a scope. If a scope is properly equatorial mounted, then to keep it
pointing at one point in the sky, once 'aimed', as the Earth moves, all
that is needed is a single motor, rotating it round the polar aligned
axis, moving at the 'sidereal' rate. This is the classic 'single drive'
configuration. However actually aiming the scope to centre an object,
requires you to move the scope in both axes. So with the single drive, you
have to take your hands off the 'controller' box, and aim the scope with
the manual controls. The dual axis drives, make this easier, by allowing
you not to touch the scope (with the vibration this introduces), and
instead just hold the controller, and move the image in the eyepiece (or
camera). The dual axis drives also allow you to do things like imaging,
where you can use electronics to control the two axes (but this is beyond
where you are working at present). In both cases, the maximum speeds of
such drives are usually slow enough, that 'gross' re-alignment (pointing
top a completely different part of the sky), is easier done with manual
movements, but once you are close to the targte, the dual axis system,
means you can keep your eye to the eyepiece, and shift an object more
easily.
No drives a all, means you have to be moving the scope all the time by
hand.
Single drive, means the scope will track to help keep an object centred.
Dual drive, means you can centre the object in the first place, using the
drives.

Best Wishes

"Roger Hamlett" wrote in message
...

No drives a all, means you have to be moving the scope all the time by
hand.
Single drive, means the scope will track to help keep an object centred.
Dual drive, means you can centre the object in the first place, using the
drives.


Is there a super cheap single drive solution for the GP/CG-5?

So far I've come up with the Vixen MT-1/SD-1, the Celestron Dual, and the
JMI 110VAC. I'm looking for something more akin to the Orion drive with the
speed control. The one they make for the EQ-1 and EQ-2, without
controller/corrector.

Thanks,
Stephen

On 25 Nov 2005 22:44:23 -0800, wrote:

We're looking at buying a telescope for our 13 year old son and are
looking at drives. What are the pros and cons of the single and dual
axis drives? What can you do with one that you can't with the other?
We're looking at the EQ-3M drives from Orion.

As noted elsewhere, dual axis drives are a primary requirement for
imaging. However, I like them also for visual use. That's because when I
use a scope visually, I'm normally exploring. So I aim at a particular
area, and then spend time sweeping it for interesting objects. Being
able to control this kind of motion from a hand paddle is very
convenient and comfortable. But to do this, your motors need to support
at least 16X tracking, preferably more. Any slower and they are really
only useful as guiding correctors- something that you don't need at all
for visual use.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

wrote:
We're looking at buying a telescope for our 13 year old son and are
looking at drives. What are the pros and cons of the single and dual
axis drives? What can you do with one that you can't with the other?
We're looking at the EQ-3M drives from Orion.

All thought are welcome.
Bill Lugg

I would say a dual axis control is particularly helpful at higher
magnifications and when the observer can not simultaneously look
through the eyepiece and reach the manual slow motion controls for the
mount.

At high magnifications, making the adjustments by slow motion controls
introducing annoying vibrations. When you can't view and adjust
simultaneously, then it's hard to center.

Assuming that, in the real world, the polar alignment may be imperfect,
having dual axis controls are nice. And I would suspect they are not
that much different in price compared to the single axis drive.
Zebra24601

wrote in message
having dual axis controls are nice. And I would suspect they are not
that much different in price compared to the single axis drive.

In fact, this is proving to be the case as I look around the web.

Personally I'm just trying to avoid any wires on my CG-5 setup. If I could
get an RA axis "logic" drive with the speed control potentiometer, I'd be
happy as a clam. I'd then add a declination slow motion control. I'd rather
spend a few minutes doing a reasonable job with rough polar alignment, than
to have a wired hand paddle. As long as I can speed up or slow down to
correct the RA, I don't mind making manual adjustments in Dec every now and
then at the low powers I intend for the mounted scope.

My other mount has dual digital drive, but I use that for imaging with an
autoguider, and for observing with a larger scope at high power.

Looks like Skywatcher might still have the single axis drive for the CG-5/GP
with 4 D-Cells and a controller. But... if I'm already going to have a wire
teathered controller, the additional wire and motor seem a small penalty,
given the benefit and the small difference in price.

Ah well...