Quote:
Originally Posted by RyanJones
Glad you got it sorted Martin
I’m a little confused. I thought your wonky stars were right across the whole field ? This might have been where an image to look at would have helped. You were over corrected then ? So forming a star shape with the cross forming a concentric circle around the whole image as opposed to blocks? You mentioned that you added more shims so this would have made the problem worse and would have made the stars more cross shaped ? Again not on axis but getting worse further from the center of the image ?
Please don’t think I’m being antagonizing, it’s not my intention. I’m breaking this down for anyone else that might be reading it to understand what they might be looking at with over corrected coma.
It’s also important for others reading to note the issue that you came across and understand what is happening here. So the faster the optics, the greater the curve in the primary mirror. Consequently the more correction required to return the image to a flat plane for the sensor. At f/6 the distance required for that correction to occur is shorter than at f/5 hence the lower spacing. There is also a limit to how fast an optic a given corrector is capable of correcting. This is why really fast optics have specific correctors made for them as opposed to multi purpose correctors. It is also worth noting that the manufacturers specifications ie. 55mm is a starting point and will likely require adjustments to properly achieve correction of each individuals optics.
I hope this has broken things down for others to understand
Cheers
Ryan
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Ryan
I think this maybe overcomplicating things by trying to analyse my issues to deeply, it’s an issue which has multiple fronts and I’ve tackled each one by trial and error with some success
And yes I did remove all my spacers last night to leave the distance at 55mm which has helped a lot , whereas a week before , I had spacers of 1.5mm and my stars were fine ( no answer at all for that scenario )
My stars are better now but still slightly off shaped on the far left hand side
Could be the coma corrector
Could be the primary mirror ( there is a slight chip on one side on the edge )
Could be the primary mirror cell holder or adjusting screws
Could be the focuser
Could be the camera
Could be ...... many things
What I can’t resolve is that a week ago my stars were fine and somehow they changed without me touching anything on the rig and it’s equipment
I don’t think my experience is of any use to others as there are so many variables and you have to work through them one at a time
No one shoe fits all with optical problems ( only the blatantly obvious)
Thanks as always for enquiring
Cheers
Martin