New WO GT81 flattener - first light

[buzz]

I finally got hold of the dedicated GT81 flattener last night and whisked off a few subs before the cirrus moved in.

I can post some CCD inspector images later, suffice to say that this really made a big difference. My stars are nice and round, right to the corners. The flattener has a 2" tube at one end and a simple T-thread at the other. It keeps the 477mm focal length of the scope. The spacing is 55-57mm and I would not disagree.

Mine was rattling upon arrival and had a load of rubbish between the elements. 5 mins later, I had disassembled, blown the dust off and re-assembled perfectly. CCD inspector was saying 17% curvature but I think some of that is a bit of tilt in the focus mount. It is amazingly different from the result without a FF. I took some flats and manipulated curves to see what the fall off was on a EOS D40 - it looked remarkably flat. This will be perfect for my wide field shots.

My remaining issue is my GT81 DDG focuser needs a redesign/rebuild. It is either slipping, or locks up, the readout goes haywire and clearly has been abandoned in the new GT81 design.

kind regards

Chris

[buzz]

First light with the combination of WO GT81 - GT81 Field flattener with the SX OAG, filter wheel and H18 sensor.

Image made with 10x10min subs. Coloured in Photoshop.