Quote:
Originally Posted by raymo
All of that is fine Gary,I didn't say that you can get perfect PA, I said as near perfection as you can get; but I stand by what I said about with the best possible DARV alignment the mount's periodic error will limit the roundness of your stars, not PA misalignment.[This does not include very expensive top end mounts, which often have very small periodic errors indeed.]
raymo
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Hi Raymo,
Thanks for the clarification.
The number of stunning images in the IceInSpace forums is also testimony
to the results people achieve in the face of the physical reality.
As Andy touched upon in the very first post, where, as i understand it,
he tweaked the OTA to mount alignment (collimation error), it touches
on what a multivariable problem alignment and tracking is.
You mention periodic error as another example.
Then there are flexures in the OTA and mount, mirror shifts, RA
to Dec non-perpendicularity and a range of other geometric and
gravitational flexure errors that are in play as well.
A more detailed analysis, beyond what can be achieved by a drift test,
is required to ascertain the magnitudes of these types of errors if it
transpires they are playing a significant role.