Quote:
Originally Posted by gregbradley
Could it be parallax error? 2 scopes slightly different views with different focal lengths and different curvature of the optics. When you overlay an image from the TEC180 does it match the TEC140 image or are there different geometries? Some alignment routines will rotate and scale for example and without that using multiple telescope images won't align properly.
Greg.
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Well, maybe!!! I use CCDStack and it automatically does rescale the TEC140 images to the TEC180 (.95 to .88 arc-sec). As far as other adjustments (it does rotate) I'm not sure. Generally my images have properly registered even though I don't have a flattener on the TEC140.
However, the effect I'm observing with the last experiment is drift observing the same guide star between the two scopes. Both scopes are looking at the exact same point in space.....only that point is being measured so as far as the fundamental principal going on here I think what might or might not be going on in the corners is perhaps a side issue (?).
Here is a though experiment I came up with. What would one observe if two guide cameras could be set up to observe two different stars through the SAME scope? In my initial experiment (first post) I observed two different stars and got a consistent drift no matter where I pointed. If the same experimnt were carried out with one telescope would we see the same drift? If "yes" then I fail to understand how "multistar" guiding can ever possibly work! But it does work as best I know, so perhaps the drift only exists between two separated scopes.
Any thoughts about this?
Peter