[Rex]

G'day everyone,
I have a HEQ5 pro and am researching scopes to put on it for astrophotography. I was thinking about a skywatcher ED80 or ED100, which I know do an ok job. But in my research I have found the GSO RC series of scopes.

I did a quick mathematical comparison using the area of the objective/ primary mirror to gauge light gathering power between a couple and was wondering if I have done this correctly.

For the ED series I basically just took the area of the objective, for the RC scopes I took the area of the primary mirror and then subtracted the area of the obstruction to get the usable area.

The results were surprising:
ED80: 5026 square mm
ED100: 7854 square mm
ED120: 11310 square mm
RC6 - 152mm primary, 76mm obstruction: 13609 square mm
RC8 - 200mm primary, 100mm obstruction: 23562 square mm

If I am correct that means the RC6 has similar light gathering power to an ED120.

Next question would an RC6 have the similar image quality as and ED scope.

Sorry to babble and thanks for your help in advance.