Hi Paul

When using the collimation viewer and setting the A,B & C knobs does the position need to change depending on where the tube is pointing. I have a GEM mount and if I'm looking directly North the 'A' would also be pointing North now if I view a Star on the East side the tube will be on the West side but now the 'A' is pointing West. I have attached a image to show an example of what I mean.

Could CCDI using a plate solve to determine where the knobs are after some sort of calibration?

Regards
-Paul

collimation.jpg (11 KB, 11 downloads) Collimation

Hi Paul,

The knobs don't need to move as you slew around the sky.

The position of the knobs shown on the collimation viewer (after you properly rotate them once) simply shows the knob position relative to the top of the OTA. Since this relationship between the top of the OTA and the knobs doesn't change as you slew around, there's no need to plate solve to determine the proper position, and there's no need to change the knob rotation.

Regards,

-Paul

Hi Paul

I was doing it right then. One of the knobs is in-line with the top of the OTA and that becomes my 'A'. I just made a complete mess of it last night. I have a LX200ACF OTA on a GEM mount and I'm using the Clock-Wise Pull (Default setting). Perhaps its my top of chip that's wrong. I've looked in the help and cannot found any reference to that. How is the top of chip determined? Also the two other choices in Screw Direction settings, Mirror Flip and Alternative In and Out is not listed in the help (or I have not found it).

Regards
-Paul

Paul,

It sounds like you are using an unsupported collimation viewer "Advisor" feature The top-of-chip display shows up only when this advisor feature is enabled. It was disabled by default a few years ago because of too much confusion over its configuration and use. The only reason it's still there is to support a few users that have figured out how to use it properly with their setup...

What I would recommend you do is to turn off the Advisor feature, and use the collimation viewer as described in the documentation. To turn it off, open collimation viewer, click anywhere inside of it, and then press Ctrl-F4. The top-of-chip indicator should disappear.

Then, simply adjust knobs to reduce the reported collimation error. At first, this will involve a bit of trial and error to determine which knob to turn.

If you are using the Single Star collimation viewer, then you'll want to adjust the knob that moves the defocused star image in the direction that the collimation viewer arrow is pointing. After a few tries, you should be able to know which knob moves in which direction, so it should be fairly easy. The A/B/C knobs displayed on the viewer are there to help you remember which knob does what.

Regards,

-Paul