Astigmatism- What happened here?
Posted 06 March 2013 - 09:33 PM
Apart from the relief and hoorays, can anyone tell me why it required rotating and gently agitating the mirror to remove the astigmatism instead of simply loosening everything?
The mirror is a plate glass substrate 14" f4.7 with good figure. Its the tropics so the difference between ambient and indoors temp is virtually nil since we use "natural ventilation"
Posted 06 March 2013 - 09:54 PM
Posted 06 March 2013 - 10:04 PM
Posted 06 March 2013 - 10:40 PM
Or the secondary has an opposite astigmatism and by rotating the mirror you managed to cancel both defects. (not likely).
Posted 06 March 2013 - 10:42 PM
You mean to say my mirror needed a good massage to destress?
I think, and others can correct me, the wedges had placed a strain on the mirror and it just took a bit of time to relax back to it original shape.
Posted 06 March 2013 - 10:57 PM
Posted 06 March 2013 - 10:58 PM
I am building a new cell for my dob, as I am waiting for a new mirror. Meanwhile the old cell was causing a lot of stig due to the hold down system. I changed to a cable sling as an experiment and things are so much better even with the old cell.
Posted 07 March 2013 - 01:56 AM