Unwanted 'warp speed' effect!!

[Beardy Bob]

Does anyone know the cause and any possible cure for stars trailing towards the edges of an image?

The stars in the centre of the image are pixel-perfect spheres and there is no 'rotation' in the star trailing (i.e. trailing in a clockwise or anti-clockwise direction), so I'm ruling out polar alignment and tracking issues. I'm therefore guessing that it is an optical effect - cheap telescope?!

I'm using a celestron C80 and a canon 350d.

[adamsp123]

Is this where you need a field flattener?

[brianb]

I'm therefore guessing that it is an optical effect

Yes. Most likely a combination of field curvature and the off axis astigmatism which two element refractors cannot correct. Field flatteners are available for many models of small 'frac, choosing the right one will do a good job of curing that "trailing".

[Beardy Bob]

I suspected a field flattener would be the cure here, but needed confirmation - thanks brian.

The obvious question now is, which one fits my setup? I had a quick look at them a while ago when I suspected that I may need one, but it wasn't obvious which model etc would be suitable or indeed where and how one would fit in the whole 'scope/camera' train. Any other C80 users out there in the know?

[jgs001]

Sorry Bob... I've just ignored it for now... a FF is on the cards at some point, but not for a while..

[adamsp123]

C80 has the same optics as a SW 80ED I believe, so you could get this Reducers/Flatteners - Skywatcher Focal Reducers but I would check with FLO.

My FF screws onto the small canon T adaptor then it slides into the focuser.

[Beardy Bob]

£150. Ouch!

[adamsp123]

£150. Ouch!

yes!

[NickH]

Try £1000 for the TMB one...if you want an ouch...