Finally I got My TPO 12" RC working.

[gvanhau (Geert)]

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

[glend (Glen)]

Thank you for your research on this problem. Isn't TPO a US brand name for GSO scopes? And thus your fix may apply to our GSO RC 12s?

[rustigsmed (Russell)]

great news Geert it must have been so frustrating - glad to hear you are up and running now (on an EQ8 yes?).

[gregbradley]

Nice work in persisting and getting to the bottom of it. These 12 inch RCs are fabulous value and this sort of work makes them a viable alternative to much more costly scopes.

Greg.

[gvanhau (Geert)]

Originally Posted by glend

Thank you for your research on this problem. Isn't TPO a US brand name for GSO scopes? And thus your fix may apply to our GSO RC 12s?

Yes they are the same telescope as the GSO.
As fa I can see, there are several minor failures in this design, but I am very happy I could finally make it work.

Geert

[gvanhau (Geert)]

Originally Posted by gregbradley

Nice work in persisting and getting to the bottom of it. These 12 inch RCs are fabulous value and this sort of work makes them a viable alternative to much more costly scopes.

Greg.

You're right , at least if you have the skills and enough patience to pursue.
I think this scope was my only alternative to get a bigger aperture than my Vixen at a reasonable price.

Geert

[gvanhau (Geert)]

Originally Posted by rustigsmed

great news Geert it must have been so frustrating - glad to hear you are up and running now (on an EQ8 yes?).

Well as you said, I was about to give up when fortunately this idea came into my mind and solved the issue. I think its going to be a wile before I touch a screw on this scope again
I'm running on top of a MI250....

Geert

[Paul Haese]

Excellent that you found the source of the problem Geert. I have not heard that this was a possible cause of pinched optics with this scope but it makes sense. Persistence has paid off for you. Congrats. If you have not already done so, get a truss for your optics. The new system has a revised back plate with incorporated collimation ring and alleviates all the weight off the mirror cell.

I have like you spent a great deal of time working on issues with these scopes and worked quite closely with GSO and Bintel on improvements that have been made. I am very happy with my RC12 and can almost say I have it singing or at least very close to producing a full tune. I will look forward to your doing likewise in the weeks and months ahead.

[Spookyer (Brett)]

Congrats, I think we all know how frustrating it is when gear doesn't work like it should. Well done.

brett

[yoda776 (Matt)]

Congrats. I certainly have empathy for the frustration you must have felt but a great reward in the end. Well done.