SCT vs. Newtonian for visual

[Ben Ritchie]

Question from a non-online friend of mine. He's looking at buying a larger-aperture telescope for visual use only, and is looking at either a 12" f/5 Newtonian or a C11 + f/6.3 reducer on a EQ6. Currently using a 100mm refractor, and is looking for a big step up in light grasp to move on to the fainter Messiers and the NGCs.

He's had a play with my 12" Dob and so has an idea what that's like, and has heard that an EQ6 can cope with the size of a 12" OTA. However, he likes the idea of the SCT for ease of mounting and eye placement, it'll all be in an observatory and i'm guessing a 12" f/5 will probably involve standing on something to view the zenith if it's on a pier whereas the SCT is convenient when seated.

I've never used a big SCT for visual, so can't really comment. The focal reducer would be permanently attached to the SCT, but even then the focal length is a bit longer than he'd prefer. Eyepieces are the set of WO UWANs (4, 7, 16 and 28mm) and WO SPLs.

As an aside, can a EQ6 cope with a 11" SCT + piggybacked refractor? That might be one way of combining wide- and narrow- fields of view.

[MikeP]

Ben,

I started with a 10" Newtonian and found it cumbersome to lift onto the EQ6. Eyepiece positions were the biggest gripe - even with the mount at its lowest I needed something to stand on and I got fed up of rotating the OTA in its tube rings.

The Newtonian went in favour of a C11 which by comparison was a breeze to lift onto the mount. No contest either with eyepiece positions.

I'm fairly sure the EQ6 will cope with a C11 with a piggy-backed refractor but others will know better.

As an opinion, if this is for visual and it will be permanently mounted in an observatory, I'd be very tempted to go with something with a fork mount. Intuitively, it seems like it would cope with the piggy back refractor better and would (intuitively again) require less space.

I'm sure others will have a different view.

Mike

[Ben Ritchie]

Thanks Mike, very useful - the Newt will be a pain to lift onto the mount, but it should be a one-time thing to get it setup and balanced. It's eye placement and general usability that's much more of a worry. Image quality with the reducer too (although admittedly you have to factor in coma correctors with the Newt).

We've discussed fork mounts, but he's not a great fan - part eye-placement at zenith again, but also he had lots of problems with an unreliable Meade fork-mount and likes the idea of two separate components rather than an all-in-one unit.

[ollypenrice]

I have had a 10 LX200 for quite a few years. The fork mount, especially Alt-Az, is indeed convenient though even, as now, on a wedge it is pretty good. But...but...I find it visually disppointing TBH. Good on the moon and planets but soft on deep sky.

I also have a cheap 6 inch Synta achromat which cost all of £400 on a mount and on deep sky it beats the SCT. Much more contrast.

How dark is your friend's site? SCTs drink up light pollution. And how dry? You know why I'm asking that! My feeling is that you are boxed in by the long focal length and treated to a somewhat inconclusive view. But they are handy.

Olly.

[beetlejuice]

I agree with Olly. SCT's are very convenient to mount and store, but they just aren't in the same league as a well collimated Newt, or a good quality refractor, for deepsky. Focus is never as sharp on dso's as | would like despite careful collimation. That said, I'm not getting rid of mine any time soon......but a big dob is next on my list!