I use 6, 8 and 10 newts ( f5 and f6 ) for imaging ( Bintel which is in fact GSO brand)
Yes you will need a coma corrector
If the budget can stretch a bit , thoroughly recommend the TS Optics GPU coma corrector available from Sidereal Trading in Melbourne. I used a Baader Mk3 coma corrector for many years and could never eliminate coma totally plus its a little flimsy thing which has a very narrow ring to butt up into your focuser , I also had tilt issues with this thing.
The TS Optics GPU is a quality optical accessory and does the job perfectly at f4 up to f6. The only thing to be aware of is it may introduce some Vignetting into your image train but is easily rectified with calibration frames ( flats )
Extremely happy with the TS Optics GPU CC ( recommended by Diego from Sidereal, very experienced Newtonian imager and telescope builder )
Cheers
Martin
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