Which focal reducer best for astrphotography? 3.3 or 6.3?

[evilgeenius]

Hi

Which focal reducer would be better, a f3.3 or a f6.3? I have a CPC 925 and don't have a wedge yet, but plan to get one at some point.

I've learnt that the lower the f, the lower exposure time required when taking a photo. Why is it that celestron only sell a f6.3 and not a f3.3? I'm looking at the Meade f3.3.

What is the disadvantage of a 3.3 over a 6.3?

Thanks

Chris

[Merlin66]

The x0.63 is the way to go.

The x0.33 is only for very small chips (webcam) and really doesn't work to well - the back focus distance is very critical.

Just go for the tried and proven x0.63

[Psychobilly]

I Agree with Ken, I have both.. the f3.3 was a moment of madness purchase...

[ollypenrice]

I got no sense out of the 3.3 either and was only given it because the owner couldn't either!! They really should stop selling these things or make it clear that they are only for tiny chips.

Olly

[Peter Drew]

Bucking the trend , I've had great Watec 120n DSO performance with a 12" SCT using the F3.3 and the F6.3, the F3.3 images were always brighter and better focused. It's important to get the spacings correct in either case.