Help needed with new flattener.

[batema]

Hi,

I have had a spacer made for my Williams Optics Flt 110 Pflat68 to the QHY9. I did LRGB of the Swan and thought the focus was a bit soft but did not know if that was the seeing. Anyway last night all I managed was 2 x 20 Min Ha of the Lagoon. It appears to have got bigger in my image as opposed to prior to my flattener and I ended up with eggy stars but the all are oval shaped from right to left not corner to center. Any advice on what could be going on would be helpful unless as I rotated the camera using the 360 degree rotator but still focussed after that could be the issue. Of course it is cloudy tonight. A rough Lagoon.

Mark

[cybereye]

I had issues like this and it was due to flex issues between my guidescope and main scope. You could do a trial of with and without the field flattener to rule that out...

Cheers,
Mario

[[1ponders]]

I'd agree with Mario Mark. Oblong in one direction (horizontal, vertical or oblique) would seem to indicate flexure of some sort. If the FR is the only new thing in the train then I'd be looking where it inserts into the focuser. As Mario suggestion, remove the FR and see if the motion goes away.

[ozstronomer]

Mark,

You may have seen this diagram showing chip distance

http://www.williamoptics.com/accessories/images/TMBflattener_ChiptoLens.jpg

Mine is flat with the Marovian CCD camera at the suggested distance.

Also I found with the Gold ring that the flattener attaches to I had to adjust the three grub screws so the ring was A) centred in the optical train and B) each screw is equally screwed in, this sorts out A) above.

Even with this done, If I have rotated the camera, I always push it up hard against the back end before I re tighten to assure the camera chip is as square as possible to the optical train.

Cheers Geoff

[gbeal]

I'd be inclined to try a bright star cluster, M7 or similar, and keep the exposures as short as you can, you're not looking for deep and dark, merely to see that the stars are round or otherwise. Keeping the subs short means less flex, less tracking etc.
Gary