ZWO 2600 with Z73 0.8 Focal Reducer

[smr]

Hi,

I'm thinking of buying the ZWO 2600MC Pro with the Zenithstar 73 0.8 Focal Reducer.

If my Maths is correct this should provide a 344mm focal length (430mm x 0.8) and an f ratio of 4.72. Is this much faster in terms of light gathering than 5.9? 

The actual fov isn't drastically different. If I took images with the focal reducer and then cropped in to the 430mm focal length fov of the scope, would there be the same sort of detail being that more light has been gathered ?

I wouldn't want to crop in all the time anyway, there are plenty of targets which would benefit from a wider fov such as the Witches Head which would be framed more nicely etc.

Also would there be any other things to think about when imaging with the focal reducer and this Camera? Would there be any vignetting ?

Here's the fov at 430mm

 

And with the 0.8 reducer at 344mm