Using a CCD - Do you use a focal reducer?

[swag72]

With my DSLR attached to my SW120 ED I use a x0.85 focal reducer that effectively brings my 900mm focal length down to about 765mm. I understand that it is best to use this to reduce all sorts of nasties towards the edges of the view.

With a CCD, do you use a focal reducer? Or do you plug it straight into the focuser so that my SW120 ED would still be 900mm?

[Catanonia]

same setup, just replace the DSLR with the CCD using the right adapters and spacing.

[Whippy]

It depends really. What you're got Sara is a focal reducer and field flattener so not only does it reduce the focal length but also flattens the field of view so it gives you those pinpoint stars from edge to edge.

Flatteners are more necessary when you're using cameras with larger chip like DSLR's, whereas cameras like mine with their smaller chips manage to get away without using one most cases. Focal reducers reduce the focal length and therefore focal ratio so it makes your scope faster. You can buy reducers that don't flatten the field same you can buy flatteners that don't reduce.

I use a william optics FFII on my ED80 purely to make the field slightly larger and make the scope faster. The field is flat enough with my camera without it.

Tony..

[martin_h]

I have the SW 100 and 80 ED and use the reducer on both with a larg(ish) chip CCD.

Like has been stated it is a flatener as well, so corrects to edge of the frame....If you use a small chip CCD you might get away without the reducer but it will increase the f ratio - so swings and roundabouts - as always !