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How to best balance a newtonian on an eq mount?

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#1 pesa


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Posted 06 September 2013 - 04:51 PM

Since I'm making my mounting attachement on my newtonian permanent I thought I'd better make it correct...
Many Pictures of newtonian astrographs - ASA, Orion optics and others - shows the tube attached to the mount in such a way that camera hangs straight down when mount is in home position. Is there some advantage to that balancing-wise or other.
It feels a Little insecure to have filter Wheel/guider/camera hanging like that; even if I make some security Cable so the stuff doesnt drop on ground it could easyly drop just a Little.

#2 Datapanic



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Posted 07 September 2013 - 05:00 PM

I think that the best way to balance a newt on an eq mount is to start off with balancing the OTA with tube weights first, then balance the OTA on the mount. That way, no matter which way the scope is pointed or rotated or what kind of equipment is attached to it, the balance is there and you don't have to mess with working around the problem.

#3 David Pavlich

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Posted 07 September 2013 - 09:49 PM

The camera down in home position is pretty much the universal way to do it. Here's how I balanced a Newt on a GEM:

First, set the RA axis horizontally and balance the OTA (Dec axis) in that plane.

Next, balance the RA axis in two ways: for imaging in the East, balance it slightly counterweight heavy and mark the counterweight shaft. I use electrical tape. Now, do a flip and balance the RA axis slightly scope heavy and, once again, mark it. Now you know where the counterweights need to be positioned depending on which side of the meridian you are working on. Doing this ensures that the worm gear stays engaged.

Now comes the fun. Place the RA axis horizontally and point the scope vertically. Now balance it that way. This will require that you rotate the OTA one way or the other until you let go of the scope and it remains in the vertical.

Lock it down and you should be fine.

#4 plav1959


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Posted 08 September 2013 - 03:33 PM

It will require an extra ring, but this is the easiest and quickest way I've found:

#5 jbalsam


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Posted 12 September 2013 - 11:24 AM

For the scope to be balanced, the center of gravity (CG) needs to be in the plane defined by the two rotational axes. If you have the focuser of the newt projecting from the side of the scope away from that plane, it's shifting the CG away from that plane. Adding more weight (camera, etc) to the focuser increases this shift, making balance impossible via the normal procedure (i.e. just shifting the scope fore and aft and moving counterweights). As the fellow from astronomy shed demonstrates, you have to be concerned with the scope rotation in order to get the CG located on the plane of the axes. If you didn't want to rotate the scope for some reason, and your mount can take some extra weight, you could also just strap some weight on the side of the scope opposite your focuser drawtube. This accomplishes the same thing: shifting the CG towards the plane of the axes.

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