faulksy Posted October 9, 2011 Share Posted October 9, 2011 what does on and off axis mean, have heard it mentioned a lot on here whan talking about ep:confused: Link to comment Share on other sites More sharing options...
Merlin66 Posted October 9, 2011 Share Posted October 9, 2011 On axis, just means "on the optical axis" - for all intent and purposes the exact centre of the field of view...off -axis is anywhere towards the edge of the field of view...HTH Link to comment Share on other sites More sharing options...
robbieince Posted October 9, 2011 Share Posted October 9, 2011 On axis means central to field of view - assuming everthing is collimated - so its the focus at the centre of your eyepiece / camera view, effectively.Off axis in this context means at the edges of your filed of view - typically where optical errors show up, ie coma and astigmatism.A poor optical set up will show a decent image on axis but will show up distortions nearer the edge of the field of view Link to comment Share on other sites More sharing options...
brantuk Posted October 9, 2011 Share Posted October 9, 2011 Off axis guiders allow you to image through the main axis of the scope with an additional camera on the side where you can put a guide cam. This receives an image from the edge of the field of view produced by a small diagonal mirror poked into the edge of the light train. Sometimes the diagonal is rotatable around all or part of the image edges. Here you can pick a star to guide by through the same optical setup and reduce drastically any flexure Link to comment Share on other sites More sharing options...
faulksy Posted October 9, 2011 Author Share Posted October 9, 2011 thanks to all 3 for clearing that up. wanted to ask for a while but hoped someone else would then i could read there post lol. thanks chaps Link to comment Share on other sites More sharing options...
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