what lens for afocal astrophotography

Started Mar 1, 2013 | Discussions thread
Pete Berry Senior Member • Posts: 2,946
Re: what lens for afocal astrophotography

t_andersen wrote:

I have designed professional telescopes for over 30 years and I agree with the other guys. Don't take images through an eyepiece. Get a relay lens, i.e. a focal extender as suggested above, and put your camera in the second focus.

But for highest resolution planetary images w/ amateur scopes, you need a much larger image than the above can generate - and the small sensor of webcam or camcorder still seems the best way. I've used a C-9.25 scope w/3X Barlow, afocally coupled to a 3-CCD camcorder through a dedicated afocal imaging eyepiece for ridiculosly long EFL when zoomed in, eg Jupiter about 3/5 of frame height. Full manual controls, including low shutter speeds and independant aperture and gain are needed. Zooming out is most helpful in object finding.

Here's a link to some images, with albums of hi-res stacked video frame planetary images, and solar eclipse imaging of chromosphere and individual flares in white light with a 4" MCT (single frames). All components are solidly connected on an in-line simple rail:



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