Focal Reducers

[AstroTom]

Hi everyone,

I own a celestron cpc 800 telescope which is f/10. I also own a focal reducer which reduces the scope to f/6.3. I was wondering if there are any other focal reducers available for reducing my focal length further say to f/4.

Also has anyone thought of putting focal reducers in series? I don't expect it to work and I don't want to buy multiple reducers to experiment to see what happens but interesting to know if anyone would know the outcome of doing this.

Anyway would be interested to find out about the above.

Regards,

Tom

[blink138]

you can modify it through a system called hyperstar, easy to google which will bring your system down to f2!
pat

[jenchris]

Reducers are pretty specific and even have particular scopes in mind - I believe there's even a 3.3 available for that scope.
A bit different for the edge ones though (and ACF Meade) as the field flattener is not needed and comes as part of the FR.
AP make one but it's not cheap!

[Camelopardalis]

There is usually some penalty to shortening the light cone...it's already evident with the f/6.3 reducer, as there isn't as much back focus as at regular f/10, to the point where some eyepieces (mostly 2" ones) won't come to focus.
Then you reach a point where the baffle tube cuts into the light cone and causes vignetting.

In practice, I've found that the best way to maximise the FOV of my C8 is to use a 2" long focal length eyepiece, such as a 40mm Paragon, which works really well for about 1.4 degrees. Any objects that don't fit in that are probably better viewed in a very short focal length refractor IMO.

Meade currently produces a native f/8 SCT and have promised a reducer taking it down to f/5, but it has yet to go on sale. The down side of the shorter native focal ratio is the secondary obstruction is noticeably bigger than the f/10 models. There's much debate about how this would affect the image but very few posts about the real experience with the scopes themselves...so far, they're pretty recent additions to the range.

[AstroTom]

Thanks everyone for the advice. I think for now I'll just stick with my focal reducer and my telescope as is. I'll bare in mind all your advice when I do start to look into this again.

Thanks again, Tom