[CalvinKlein (Kelvin)]

I am considering buying an inexpensive 10" F4 Newtonian mainly for capturing the ISS and for tracked planetary imaging. Until now I've quite successfully used a 7" triplet refractor for each but need more aperture for the ISS.

I use a Televue Powermate 4x and ASI183MC for the imaging.

Can anyone give me an indication of how much of the Field of View is totally useless due to coma -ideally with sample images.

For manual ISS tracking ideally its good to utilise the entire sensor but if, say, the centre 30% remains sharp-ish and the rest coma affected - that might still be acceptable - any less would be too difficult to get centred.

Thanks