f6.3 reducer question

[northcanadian]

Hi all: 

I hope this question isn't too beyond the pale.....I have an f10 sct. If I use the f6.3 reducer/corrector and bring it down to f6.3 would there be any advantage regarding faster planetary frame rates ?

A 2x barlow would be f12.6 rather than f20?  A 3x barlow would be f18.9 rather than f30, etc., ....just wondering if faster frame rates would be generated or if there would be any relevance?

Thanks again

Cheers

Roger

[riklaunim]

There is no point of using focal reducers for planetary imaging where you need longer focal lengths. If you want less than 2x magnification then use Baader Q-Barlow or 1,25" lens from 1,25" GSO/Revelation Barlow. Achieving f/15 without reducer or with reducer and a stronger Barlow will yield the same brightness.

And those reducers may add some chromatic aberration (+Barlow and you may get bad image quality).

[jambouk]

Do you mean you'd potentially be able to achieve faster frame rates (given fixed gain settings) because the target would be brighter and you could reduce the exposure time?

I'm not sure, but the target would be smaller, and there is a lot of glass in a reducer so one would lose some light in that.

The other consideration is that the reducer is also a flattener and requires a fixed distance from the reducer to the imaging sensor, and i'm unsure how this would be affected by adding barlows into the light path; i'm unclear what distortion, if any, this would introduce in the centre of the FoV where presumably you would put the planet.

What sort of frame rate are you managing to achieve at present? With what camera?

I suspect you'd be better to just wait for a night of excellent seeing and just capture data at 30fps with excellent focus.

Good luck.

James