Quattro CF Collimation problem solved

[gazza]

Hi,

I have an 8" Quattro F4 CF.

For a while I struggled getting it to work correctly (ie get nice images to the edge of a KAF8300) using the Skywatcher/GPU coma corector.

After several months I got it working properly, then a took it off the mount for a while as I wanted to use another OTA. When I put it back I was unable to get a good field and struggled with it for months. I did every mod that was suggested for it to no avail. I literally was ready to take an axe to it. (Frustration with it was actually why I bought an Esprit 100!)

Nothing was consistent, I ended up doubting everything including myself.

Suddenly the penny dropped.

I measured the adapter that screws in to the top of the focuser. A caliper showed it to be oversize slightly. This meant that the long coma corrector was able to tilt somewhere around 1/2  degree. It also meant the camera would never sit in the focuser the same way twice - hence my variable results, even though I would try to collimate at every session.

A machinist friend offered to make me a close tolerance adapter for the focuser (pictured alongside the original.) It was made longer to provide more support and resist tilt better.

The very first time I used after collimating, my pictures were perfect to the edge! Problem solved - crappy 2" adapter.

If you are having issues with a fast newt, you might want to check this.

Hope it helps and saves someone the months of frustration I had.

cheers

Gary