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Using a fisheye lens for widefield imaging


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My local camera shop has an 8mm fixed lens on for a bit of a bargin price and I am sorely tempted, on my camera it would provide a 167o field of view. However being a fisheye lens it is inevitably heavilly distorted, so my question is: is it viable to leave such a lens snapping away all night and then use deep sky stacker to stack the results or would it have to go on a driven equitorial of some sort to prevent field rotation?

any thoughts or experiences welcome...

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I have a Peleng 8mm 'fish eye' - its not quite 180 degrees in an APS sensor camera, though.

I'm pretty happy with the results from it so far, but only really had a couple of sessions with it.

You'll not see trailing on 30s -> 1 or 2 mins. And i have had some success with adding the subs together (in IRIS). If you wanted to expose longer, though, you would want a tracking mount.

Field rotation will become an issue, as will edge effects as you increase the number of subs.

/callump

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I also have an Peleng 8mm fish eye and have been surprised at how quickly training becomes an issue, I can't go longer than 45 seconds before trailing is noticeable.

As for whether you use a tracking mount during a long imaging session, I think it is probably best then use a a single shot for the non celestial part of the shot taken at the start of the session. You could use a static mount and I believe DSS will be able to handle the field rotation.

I use RectFish to convert the fisheye view into rectilinear. Works very well but it costs about £30

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I'm not really bothered about trailing, I know how to deal with that, what I was wondering about is whether the inherient distortion of the lens would make it impossible to stack images given that unless the camera is tracking the stars will change position in the frame from shot to shot, this plus the distortion will cause apprent changes in geometry, the real question is: can DSS recognise and work with these distortions?

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