GSO 6" f/9 Ritchey-Chretien Astrograph

[Astronutjob]

Hello seen one of these up fir sale a while ago, whats the story with these scopes i know its a ritchey chertien but why are they so cheap?, also is this a good option for astrophotography, or would i be better going with another imaging scope? are there any drawbacks with this scope over say a refractor?

[michael.h.f.wilkinson]

At F/9 they need a focal reducer to be good for deep sky. If you compare the price to that of a 6" triplet of ED you immediately spot an advantage of the GSO RC . It has a larger flat field of view than say a C6, but it is a lot heavier (5.4 for the GSO 6" vs 3.5 kg for the C6, even the C8 is only 4.7). For planetary work, the latter has the edge. I have seen some good deep sky pics made with the 6"

[Astronutjob]

so would you say a c6 would be a better option? i only intend to use it for deepsky photos, i thought it would have an advantage over a sct as there is no corrector plate (cool down time) and the primary mirror wont shift during the exposure? im not seeing many examples of people using them for imaging though?

[michael.h.f.wilkinson]

For deep sky the TV has the edge over the C6: it is a bit faster, has the flatter, larger field, and a much better focuser. At the current price (499 euro at teleskop-service) the GSO is certainly interesting.

[Astronutjob]

iv just read afew articles on people who have had one and tried a focal reducer with it and have had severe vignetting, do you think f/9 is unacceptably slow for imaging?

[Whippy]

I think it's worth pointing out that vignetting is dependant on the size of the illuminated field that the reducer has, and that varies from reducer to reducer.

Tony..