RC vs Edge HD

[petevasey]

Thanks for the heads up, Dan (?).  I used SCT's for several years without too much hassle, some imho very good images obtained.  But to be fair I'd have been in trouble without off-axis guiding, and latterly a high speed tip-tilt active optics unit from Starlight Xpress.  As you may have gathered above in this thread, I've been considering replacing both the RC10 and Meade 127 triplet with a high quality 6" refractor.  Having improved the blue halos of the Meade, see a few posts earlier in this thread, I'm happier with what I have, although of course the Meade still isn't perfect - there is a degree of star bloat with bright stars, but at least the halos are much reduced.  Nevertheless I still hanker after a really good big refractor!

I've always loved galaxy imaging as you might see from my web site, although my location is not of the best - Northern UK weather is gradually getting worse, and this early part of the year (galaxy season!) was one of the worst yet for clouds etc., even with high pressure weather patterns.  Olly Penrice reckons I could do just as well with a 1 metre 6" refractor as I do with my 2 metre 10" reflector.  Probably right - no central obstruction and slightly better seeing with the smaller aperture.  But if unbinned to get better resolution (when seeing allows) much longer imaging times.

There is one refractor which just might fit the bill - this one.  A bit 'slower' than some, but the longer focal length would help with imaging smaller objects.  Just light enough to go on my 'star party' EQ6 mount which is a bonus.  The price at the moment is very attractive.  BUT I've only been able to find images on one site, that of Wolfi Ransburg.  Pretty impressive, but there is a noticeable red edge to many stars in RGB images which is a bit worrying.  If you or anyone knows where I can find other images taken with that model of telescope, please let me know.  Interesting that he also has a 10" GSO RC!  I'm pretty sure he is one of the directors of Teleskop Service, so probably gets telescopes at a discount  😉

So as a matter of interest, which CFF refractor are you using?  Looking at your posts it would appear that you have the 8" f6.5 one?   I hadn't spotted them before on the TS site, but now I have - phew - need to win the lottery, but they look amazing!

Cheers,

Peter

Edited June 12, 2022 by petevasey
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[dan_adi]

17 hours ago, petevasey said:

 

So as a matter of interest, which CFF refractor are you using?  Looking at your posts it would appear that you have the 8" f6.5 one?   I hadn't spotted them before on the TS site, but now I have - phew - need to win the lottery, but they look amazing!

Cheers,

Peter

Yes the 8 inch f 6.5 one, oiled spaced triplet. Wonderful scope, but now I need some way to disperse clouds all year round:))

[creativspelerr]

Short of having a side by side comparison, I went to Astrobin and searched for EdgeHD 11" Jupiter and found the image of Jupiter that had the cleanest details - for instance, this one: https://www.astrobin.com/zxqjkf/?q=edge jupiter.  Now of course there's a lot more that goes into the image than just the scope (the seeing, the mount, the camera, the user's experience in processing, etc) but it means that with everything else in place, the scope is capable of producing this.  Then I searched Jupiter with other terms like like 12" Photron, GSO, Ritchey and I could not find anything that looked as good as the Edge. 

I did a similar search on the dumbbell nebula.  This was the best EdgeHD 11" I could find: https://www.astrobin.com/92m59x/?q=dumbell edgehd 11" .  And here's an RC that beats it by a little bit. https://www.astrobin.com/qlps8j/?q=dumbell GSO 12".  Of course, it has an extra inch of aperture, it's narrowband only whereas the Edge had RGB+narrowband, and other differences. 

Ring nebula on an 8" RC: https://www.astrobin.com/414858/?q=ring nebula ritchey 12" and on a 9.5" Edge https://www.astrobin.com/yanyig/B/

Looking at planetary nebulae I think they are closer to a tie and it would take digging with a fine-tooth comb to declare a winner, but for Jupiter as far as I can tell, the Edge wins. 

I have been shopping based on "What gives the crispest details with a 2500mm or more focal length," but from this comparison it looks like the the central obstruction affects planets and DSO targets differently.  An RC might outperform an Edge in some cases, but the Edge is more versatile.  Is that a fair assessment?

Edited September 7 by creativspelerr
Additional info

[vlaiv]

21 minutes ago, creativspelerr said:

I have been shopping based on "What gives the crispest details with a 2500mm or more focal length," but from this comparison it looks like the the central obstruction affects planets and DSO targets differently.  An RC might outperform an Edge in some cases, but the Edge is more versatile.  Is that a fair assessment?

Planetary work and DSO work are quite a bit different when you consider crispest details.

For planets - aperture is king and then comes central obstruction (if optical performance of the system is good - lemons excluded).

For DSO work - seeing plays a large part of the equation and central obstruction is not very relevant.

RCs have larger central obstruction than SCTs - SCT better at planetary - but for DSO work - it depends on conditions and if similar in aperture, both will produce similar results.