SCT Balance -- Fork Weights?

I have seen a number of photos in which there is a weight of some sort
on either fork arm of an SCT. Is this necessary for a 'scope that is
used within a few degrees of the meridian? Am I correct in assuming
that the weight is placed on the west arm if the 'scope is inclined
significantly to the east and vice-versa? TIA!

Davoud

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usenet *at* davidillig dawt com

On Fri, 25 Mar 2005 12:35:04 -0500, Davoud wrote:

I have seen a number of photos in which there is a weight of some sort
on either fork arm of an SCT. Is this necessary for a 'scope that is
used within a few degrees of the meridian? Am I correct in assuming
that the weight is placed on the west arm if the 'scope is inclined
significantly to the east and vice-versa? TIA!

Davoud-

The weight is important with most fork mounts. You want the east side
heavier than the west side. This is so that the RA drive is always
pushing towards the west, rather than pulling. If you are pulling,
stiction can cause the motion to stop and start.

At least with Meade mounts, the declination motor is on the west side,
so these mounts are naturally heavier on that side. It takes several
pounds on the east arm to offset this and ensure good guiding.

_________________________________________________

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

Davoud:
I have seen a number of photos in which there is a weight of some sort
on either fork arm of an SCT. Is this necessary for a 'scope that is
used within a few degrees of the meridian? Am I correct in assuming
that the weight is placed on the west arm if the 'scope is inclined
significantly to the east and vice-versa? TIA!

Chris L Peterson:
The weight is important with most fork mounts. You want the east side
heavier than the west side. This is so that the RA drive is always
pushing towards the west, rather than pulling. If you are pulling,
stiction can cause the motion to stop and start.

At least with Meade mounts, the declination motor is on the west side,
so these mounts are naturally heavier on that side. It takes several
pounds on the east arm to offset this and ensure good guiding.

Thanks for the elucidation. I read from the pushing-pulling information
that a weight is desirable even if the 'scope is used over a fairly
narrow range of R.A.'s near the meridian. Now to decide what to use as
a weight.

Thanks again,

Davoud

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usenet *at* davidillig dawt com