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Thread: Paracorr on F/4 vs F/5 Dob

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    Default Paracorr on F/4 vs F/5 Dob



    Hello everyone! I've been catching up on the focal ratio debate, but what I can't find are comments on how an F/4 performs visually vs an F/5, both with a paracorr. I've seen the numbers, but I couldn't find a real-life visual comparison...would the F/5 be visually better, or will the paracorr in effect get rid of coma on the F/4 just as well (visually, not technically)? If I were to look at both scopes with a paracorr, would I pick the F/5 as the better performer?

    I'm looking at this because I'm considering a build with a larger F/4, but have only used scopes as fast as 4.5, and only minimally. I'm debating btw something like a 17.5" F/4, a 15" F/4.5, or a 12.5/13" F/5. I'll be catching planets in the yard and those DSO's at a dark site.

    As always, your feedback is most appreciated. Thanks!

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    Default Re: Paracorr on F/4 vs F/5 Dob

    I have never used an f/5 scope, but I have an 8" f/4 Newt with a Paracorr. With the Paracorr and quality eyepieces (Panoptic), the view is superb, with no trace of coma. With the Paracorr and cheap eyepieces (Antares W70), the view is still good. The edges are a bit ratty, but the rattiness doesn't look like coma. It is probably just an artifact of the cheap eyepiece.

    Without the Paracorr, the Panoptic still performs well, though there is a hint of fuzziness at the edges. And without the Paracorr, the cheap eyepieces are truly horrible everywhere except at the centre.
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    Default Re: Paracorr on F/4 vs F/5 Dob

    Quote Originally Posted by KeithBC View Post
    I have never used an f/5 scope, but I have an 8" f/4 Newt with a Paracorr. With the Paracorr and quality eyepieces (Panoptic), the view is superb, with no trace of coma. With the Paracorr and cheap eyepieces (Antares W70), the view is still good. The edges are a bit ratty, but the rattiness doesn't look like coma. It is probably just an artifact of the cheap eyepiece.

    Without the Paracorr, the Panoptic still performs well, though there is a hint of fuzziness at the edges. And without the Paracorr, the cheap eyepieces are truly horrible everywhere except at the centre.
    Thanks, Keith! My EP collection is strictly Explore Scientific 82 degree, so I hope they'll be okay. Either way, you helped to remove my doubt about fast dobs.

 

 

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