gvanhau
20-03-2015, 11:48 PM
Hello
I was about to give up, because nothing solved the triangular shaped stars coming out of my 12" RC.
The last thing I did before finding the solution, was to completely remove the retention clips from the primary mirror, because they were generating some spikes that could derive in the triangular shaped stars, but that did not help at all.
Then I wrote to Rod at OPT telling what was happening and told him that if he had no other test that could be done, my only option was to return the scope.
Rod answered that most of the problems with this RC's were to much pressure on the secondary colimation screws.
I then tried loosening these screws to a minimum, jut not allowing the mirror to move by gravity....But nothing happened, still the same odd shaped stars.
As a last desperate intent, last night I disassembled the secondary mirror cell.
The cell has metal cap screwed on the back, with almost 1cm spacing between the mirror and the back plate, so I find it verry difficult that the presure of the screws on the plate can deform the cell and cause pinching.
The mirror is separated from the cell in the back by six cork pads (or some other material) and is retained on the top by a metal screwed retaining ring. (I suppose there is some rubber ring between the mirror an the metal retaining ring, but did not verify that.)
So, what if I slightly loose the screwed retaining ring?
Fortunately I could move the ring by hand with some effort, and left it just touching the mirror.
After that, I re mounted the cell and colimated the scope.
Then did some imaging test, and for the first time in almost a year,
I could see some nice round stars coming out.
Geert
I was about to give up, because nothing solved the triangular shaped stars coming out of my 12" RC.
The last thing I did before finding the solution, was to completely remove the retention clips from the primary mirror, because they were generating some spikes that could derive in the triangular shaped stars, but that did not help at all.
Then I wrote to Rod at OPT telling what was happening and told him that if he had no other test that could be done, my only option was to return the scope.
Rod answered that most of the problems with this RC's were to much pressure on the secondary colimation screws.
I then tried loosening these screws to a minimum, jut not allowing the mirror to move by gravity....But nothing happened, still the same odd shaped stars.
As a last desperate intent, last night I disassembled the secondary mirror cell.
The cell has metal cap screwed on the back, with almost 1cm spacing between the mirror and the back plate, so I find it verry difficult that the presure of the screws on the plate can deform the cell and cause pinching.
The mirror is separated from the cell in the back by six cork pads (or some other material) and is retained on the top by a metal screwed retaining ring. (I suppose there is some rubber ring between the mirror an the metal retaining ring, but did not verify that.)
So, what if I slightly loose the screwed retaining ring?
Fortunately I could move the ring by hand with some effort, and left it just touching the mirror.
After that, I re mounted the cell and colimated the scope.
Then did some imaging test, and for the first time in almost a year,
I could see some nice round stars coming out.
Geert