I have been using my TAK Epsilon 130D together with an ASI 6200MM camera for more than a year now. I have learned to collimate the telescope the TAK way. Its easy and straightforward, and the collimation is rock solid, as long as one does not rotate the focuser. This is all well known in the community.
I have also found a significant tilt in my optical train. I bought the big CTU (camara tilting unit) by Astronomik/Gerd Neumann to deal with it and spent many clear nights trying to find the right setting to get round stars - and I think I have some revealing results:
- The tilt is not due to the camera sensor and not due to the optical train after the field flattener, since I got the same tilt with two totally different optical trains (including the camera)
- The tilt is huge. I did achieve round stars, but at the maximum possible tilt you can set with the CTU, and that is 1mm on the one side, and 0mm on the other !
- I found this puzzling, since such a huge tilt should be easily visible when looking at the components of the optical train, but it is not.
Finally I am confident that I found the reason for the tilt. The inner drawtube of the TAK focuser is tilted w.r.t. the outer tube. By collimating you can center the optical axis on the center of the sensor. But due to the tilt of the drawtube, the sensor remains tilted w.r.t the optical axis. The tilt of the drawtube can easily by seen when rotating the focuser during collimation: The point where the axis of the drawtube touches the secondary mirror moves by about 2mm during the rotation.
This means that the well-known problem that the Epsilons do not stay collimated when the focuser is rotated, always comes with this tilt. It has the same origin - the crappy focuser of the Epsilons.
I am writing this so that it may be useful to some Epsilon users. But also because I am looking for a solution.
One rather adventurous path might be to disassemble the focuser and somehow try to fix it. I heard that the inner drawtube is running on teflon coated pads of some kind, and the problem is created because the pads dont have the same size. Has someone ever had a look at this ?
I know that there are other focusers for the Epsilons on the market. Unfortunatelly, Moonlite has decided to sell their focuser with a build-in stepper motor only. This is incompatilble with my setup including the ASIAIR. Since my observatory is remote controlled and the ASIAIR in my opinion is the best, most user-friendly solution for this, I am not willing to sacrify it for the Moonlite focuser.
Other focusers for the Epsilons are rare, so I am curious if someone has an alternative focuser up and running on an Epsilon with good results ?
Edited by p088gll, 26 March 2022 - 04:43 PM.