[avandonk]

I was having flexure problems when guiding with the 100ED.

I bolted a Tal finderscope FL 185 mm to the camera frame and with some bits I had mounted the Lodestar very solidly where the eyepiece was. See image one below.

It guided very well and all my flexure problems were gone as now the camera was effectively being guided.

You can see the field of the guidescope on the imaging scope in image two. Followed by both the imaging scope field and the corresponding field of the guidescope.

The last image is a screen grab of MaximDL The RMS errors are 0.062 and 0.039 pixels of the Lodestar binned X2!

The Lodestar x2 binned pixels are 18'. This means the RMS guiding is about 1'. (0.062 X18' = 1.116').

The imaging scope pixels are 3.1'. So guiding with a 185mm FL optic is giving me about a third of a pixel guiding accuracy.

The 0.3 sec exposure of the Lodestar is smoothing out some seeing.

I had to do this experiment and calculation as my mind refused to believe that a 185mm finder can guide a 600mm imaging telescope to sub pixel accuracy.

Other guiding software such as PHD also are capable of tiny fractions of pixel accuracy.

Bert