GSO 8" f/12 Classical Cassegrain - A worthy Upgrade over GSO 6 inch RC ?

GSO 8" f/12 Classical Cassegrain iOptron iEQ45 Reflectors Buying Advice
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Abhijit Juvekar avatar
Abhijit Juvekar avatar
Hi,

I am thinking of getting GSO 8 inch Classical Cassegrain OTA.

will it be a worthy upgrade over 6 inch RC, that I currently have?

I have seen planetary imaging limits on 6 inch RC, but it is ok for DSO.

Will the Classical Cassegrain give good results for DSO as well if used with 0.67X reducer?

OPTION 2 -
In the past I used Sky-watcher 10 inch Dob and it given super results for Lunar and Planetary imaging due to big aperture.
But it was too heavy and limit for my current mount iOptron iEQ45-Pro.

So, I was thinking of getting Sky-watcher 8-inch manual Dob and use it's OTA (by adding dovetail and Tube rings) with my current mount for DSO and planets.

What say?

P.S.
I can't afford Celestron C8 in India as prices are too high due to import duty+Taxes.

Thanks!
dkamen avatar
dkamen avatar
The reducer is a bad idea. The CC is best used natively (few good reducers out there, if any) and will be an upgrade for planets and for small bright DSOs such as planetary nebulae. For extended objects, the RC is better and if you wanted to upgrade you should to a 8" RC.
andrea tasselli avatar
andrea tasselli avatar
Your best bet is still Option 2. Use it with a coma corrector for all sorts of DSO and switch to a barlow 3x for planets. You can't do that with either RC or CC.
Abhijit Juvekar avatar
Abhijit Juvekar avatar
The reducer is a bad idea. The CC is best used natively (few good reducers out there, if any) and will be an upgrade for planets and for small bright DSOs such as planetary nebulae. For extended objects, the RC is better and if you wanted to upgrade you should to a 8" RC.

*** But isn't that 2 inch aperture increase much small step up?  How big it will improve the results?  ***
andrea tasselli avatar
andrea tasselli avatar
77.8%, at the same image scale. So nearly an entire f-stop.
dkamen avatar
dkamen avatar
And by the way that holds regardless of scope type. 8" is 8", meaning considerably better light collection and resolving capacity than 6".

Of course this is just one of many, many factors that determine how a scope will perform.

One thing I don't understand is why get a 8" Dob and not just a tube to start with? Like the 200P Quattro, if you like Skywatcher? That way you won't pay to get extra rings neither will you pay for the Dobsonian base. And Dobs are usually optimised for visual, not photography (although this could be more of a marketing thing).
Helpful
andrea tasselli avatar
andrea tasselli avatar
Except for the secondary mirror/support shading effects:

25% of Primary diameter = -6.25%

33% of Primary diameter = -11%

50% of Primary diameter = -25%
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