What is the best 8 inch SCT OTA?

[Guest]

Over the years I have had three SCT telescopes. The first being a year 2000 American made LX 90 with fork mount. Then an older C8 and after this an orange C8 from an SE setup. I could never get on with the orange tube. It had Bob's knob's so was always collimated,but never really gave good views of anything.

The older C8 was promising,but I never enjoyed using it with my then GOTO mount. At the time all's I can remember was fiddling around trying to get the GOTO to work and dew pouring from

the can can and mount while friends were waiting for a view. Unfairly can the telescope I sold it in frustration. The LX 90 gave great views and I wish that I had kept it.

I have recently bought a deformed 6 inch Meade act SCT.This OTA is heavy compared to other act's and the spec's confirm this. But mounted on my Altair Sabre alt/as mount is a joy. I am now thinking of looking for an 8 inch version. Any advice on which SCT 8 inch that I should get would be welcome. I have heard it said that early 2000's American made Meade or Celestron 8 inch act's were good.

I just want a good 8 inch sctthat gives good views of all objects.

[damnut]

Hi Martin,

How were the views out of the deformed OTA .. I had a 10" Lx200 and it was absolutely fab. I think most of the modern sct's are so similar you could not put a hair between em. There are some bargains to be had if you want the ota alone, there is a 10" at £599 on asb&s and 8" I have seen from £400-£500

[nightfisher]

Hmm, maybe i should sell the darn lot and get a 10" sct, i hear good things about the meade sct`s

[Peter Drew]

I also think that there is little to choose between them visually. collimation, thermal equilibrium and seeing conditions are the main factors. My 8se gives the best views I've ever had from a 8" SCT, just lucky perhaps? 

[Dude_with_the_tube]

you are right Martian,

the early 2000 USA made SCTS where great.I have a friend who has one and even me not being an SCT fan at all ( i just dont like them in general),i was impressed with quality of views and optics in them.If you are SCT fan,deffo find one USA made.

[nightfisher]

I also think that there is little to choose between them visually. collimation, thermal equilibrium and seeing conditions are the main factors. My 8se gives the best views I've ever had from a 8" SCT, just lucky perhaps? 

Peter, i have looked through a couple of sct`s and thought they lack a little contrast compared to mak`s, do you think this is right?

[Grotemobile]

I sold my C11 last year & bought this.

http://www.firstlightoptics.com/cpc-deluxe-hd/celestron-cpc-deluxe-800-hd.html

Got to be the best scope I ever had.

I only do planetary imaging,so this  

is spot on. So easer to set up & use.

The optics, are way in front of the C11.

Sometimes bigger, is not always better,

as I found out.

Steve.

[damnut]

The 250mm sct is an excellent instrument Jule, rarely used the goto as with a wa 30mm you could swing the it round in the forks and readily acquire dso's. As for contrast, I have a 150mm mak and give me the sct anyday. But I am biased , as I have four fracs too!

[Guest]

I did have a 10 inch Meade sct but found it to be quite heavy.I may give this 6 inch a whirl fro a while .I may find something along an early American 8 inch sometime.

[Peter Drew]

Jules. There is no inherent reason why a Mak should be more contrasty than a SCT in theory, they both have similar light paths and both have central obstructions. The Maks usually have slightly smaller CO's and probably more attention is given to internal baffling which could account for perceived differences. 

[russ.will]

I must say, I'm extremely impressed with my LX200R 8". The R was the first of the ACFs (the reason for the renaming being easy Google fodder) but coincidentally also means it was an ACF that must have been made in the USA. Shortly after the re-name, production moved to Mexico and thence to who knows where.

Focus mirror-shift is so minimal, that I removed the Meade Microfocuser and the operation of everything is absolutely silky smooth. Collimation just does not budge from one night to the next. I have not fitted Bobs Knobs and was advised by a man steeped in Meade that you shouldn't (to any telescope, was his view) because they're a self fulfilling prophecy; fit knobs with plastic tips and you'll need to use them - stick with the less convenient, but far less likely to wander metal screws. 

The planetary views I'm getting on a regular basis, seem to give grist the argument that 8" is a pretty optimal do-it-all UK aperture, plus I've been really surpized by how well it does DSOs. Admittedly, it's taken averted vision, but to see the the structure within M51 ripping material from it's unfortunate neighbour was not something I was expecting. Most of all, I like the pin point stars right to the edge of field that the ACF optics deliver. Dead handy with the 9mm on M82 when there's only one faint star nearer the edge of field to finesse focus on.

I can't believe it took Celestron so long to copy ACF. <ducks for cover>

Russell

[Guest]

Hello Russell.Your last line about Celestron copying ACF. Does that mean that the normal C 8 is the equivalent to an ACF telescope?

[russ.will]

It was a bit of a joke; Meade are most often accused of copying, in particular the original C Series, like a SCT was Celestron's idea.....

No, I believe the C8 is a bog standard SCT as per the non-ACF EMC & still available 8" UHTC. The ACF introduced a (pair?) of coma correcting lenses in front of the secondary to deliver the ACF. In the Edge HD, Celestrons lenses apparently differ slightly in so far as they also claim to flatten the field, but exactly what the difference is, I'm not sure. For instance, both the ACF and Edge HD require specific focal reducers that do not flatten and therefore over-correct field curvature. Maybe Meade forgot to hype the flattening the correctors produced, which seems unlikely!

The notable difference here, is that the Edge HD flatteners are circa £600 (found a s/h example for £450) and specific to each scope, whilst Meade R/ACF owners/retailers just point at the Antares F6.3 reducer for the 8-12" scopes at about £80-90. Even Meades own reducer flattens too and appears identical to the Celestron item for the non-Edge HD scopes.

My point and the one I failed to emphasize was that the build and QC of the USA OTAs is very good indeed. I even risked the (normally heart attack inducing) no-no of shining a red light torch down my OTA in the dark and there is simply nothing to see. No smudges, sleaks, blobs, just nothing. As an ex-owner of multiple Newts, I'm not particularly fussed by such phenomena, but even I was surprized by how clean it is in there. Of course, now I'm paranoid about trying to keep it that way...

Now this also may just me being old fashioned, but the other thing I like about the LX OTAs is the overwhelming sense of heavy metal. Even the focus knob is a great big shiny chunk of aluminium, which does freeze your fingers, but is reassuringly smooth and positive. Very little back-lash and very little mirror shift. It may be just that I have a very good one, or all the USA built ones are like this, but I've seen deforked 8" Rs going for £500 and that is a lot of very nice OTA for the money. Others may prefer the sleeker visual appeal of swoopy curves, but not me.

One important thing I did forget to mention is that, in so far as I am aware, the 8" Meade is the smallest SCT (from the usual suspects) that can handle a 2" visual back. I don't know if the Celestrons can, but as I understand it, even if they can, the aperture beneath is only large enough for 1.25" accessories without severe vignetting. As I understand it, the C9.25 is the smallest 2" capable Celestron.

For me, this was an issue. It means you're stuck with a 24mm SWA (0.82deg FOV, 68deg AFOV and 85x) or 40mm Plossl (0.84deg FOV,  42deg AFOV and 51x) the latter very much feeling like looking down a bog roll. Step up to 2" and a 40mm SWA becomes a possibility with 1.36deg FOV, 68deg AFOV and 51x. That's a 39% increase in FOV and AFOV. Not small. Heck - I can get 1deg with my ES100 20mm.

YMMV, but as my primary scope, if I couldn't at least frame objects the size of M42 and the Pleiades, it was a non starter. In a C8, you won't without a focal reducer. Try the simulations in Stellarium - The difference looks bigger than the numbers suggest.

Russell

[John]

A reasonably well known reviewer once told me that, on the whole, the Celestron SCT's that he had used over the years seemed to be of better optical quality than the Meade ones that he has used. He's written for all the main UK and US astro magazines so I put some weight behind his comments.

I've only owned Celestron SCT's (two C5's and a 1990's C8 plus) and found they performed pretty well. I'm not really an SCT buff though and the above advice was given a fe wyears back now.

[russ.will]

I think I timed out on trying to edit that post. Would a mod be so kind as to delete it? I wanted to edit/add:

I had an interesting and very long conversation with a man who has spent his life servicing all makes. A man with a £25k optical flat to quantify the differences and the ability to machine components where they are no longer made; a true engineer.

He sees scopes of all vintages and makes having endured long term use and not just an insignificant sample population of personal use. He showed me the ring gear for a CPC and an LX200 and the Meade item was a good 5-6mm thick, versus the 2-3mm Celestron item. He then showed me the flattened plastic ball bearings the CPC base rides on. Why flattened? They can't cope with running on a wedge. Interestingly, he said that there was stuff all in it optically, but if you want to mount a big fork in a society/club observatory, there are good reasons why you see more Meades.

What was also interesting was that he runs a Celestron EQ mount and an 8" LX200 ACF OTA. He said he couldn't see the point of going larger if you wanted consistent views under UK skies. From the only man that SPM allowed to service his optics, that put's some weight behind his comments.

The only thing that seems certain is that there are as many opinions on the subject of Meade v Celestron as there are users/reviewers. There are at least as many people happy with their scopes, as there are people willing to diss the other. You see awesome images taken by both, which seems to be the acid test. 

Back on track: Whilst trying to clarify what makes an ACF different from an Edge HD (Answer: Aspherized secondary verses two lense elements - I was WAY out) I came across this. Interesting corrector plate issues those and inconsistent with the second sample. Actually, whilst that site is a bit of a mess to navigate in general, the results for a number of well thought of scopes make interesting reading (scroll down the tests), not least because in some instances he tests multiple versions of the same mirrors/lenses of some fairly vanilla fayre that measure very well. It really makes me want an FSQ106.....

Russell

[John]

I think I timed out on trying to edit that post. Would a mod be so kind as to delete it? I wanted to edit/add....

I've deleted your earlier partial post Russell.

I think I've met the chap you are referring to as well

[russ.will]

Thank you and quite probably; he's no secret. Pleasingly, he's almost as grump as me and has impeccable taste in rock music.

Russell

[dweller25]

@Grumpymartian - take a close look at the Intes Micro 715 - well baffled for high contrast, 25% central obstruction, minimum 1/6th wave and a cooling fan that pulls air across the primary to remove the boundary layer. I have had a C8 and a C9.25 and neither matched the performance of the IM715.

[John]

Thank you and quite probably; he's no secret. Pleasingly, he's almost as grump as me and has impeccable taste in rock music.

Russell

Being a grump and a taste for rock music must go together then, or so my wife tells me. I can't seem to grow out of either

[Guest]

Well I bought  Celestron C5 and I am very happy with it's overall appearance and build quality.

[Chris]

I sold my C11 last year & bought this.

http://www.firstlightoptics.com/cpc-deluxe-hd/celestron-cpc-deluxe-800-hd.html

Got to be the best scope I ever had.

I only do planetary imaging,so this  

is spot on. So easer to set up & use.

The optics, are way in front of the C11.

Sometimes bigger, is not always better,

as I found out.

Steve.

I bought an Edge after hearing you rave on about them, now I've joined in raving on about them!

[Marki]

I also think that there is little to choose between them visually. collimation, thermal equilibrium and seeing conditions are the main factors. My 8se gives the best views I've ever had from a 8" SCT, just lucky perhaps? 

Really wish I hadn't sold my 8SE...great piece of kit. Well, the OTA was excellent, especially when I started to use it with my AZEQ6GT (much quieter than the SE mount). The red dot finder it came with was absolutely pants though!

[nightfisher]

Really wish I hadn't sold my 8SE...great piece of kit. Well, the OTA was excellent, especially when I started to use it with my AZEQ6GT (much quieter than the SE mount). The red dot finder it came with was absolutely pants though!

I keep coming back to the idea of selling about 3 scopes and getting a c8 or meade 8"

[Joves]

I think a decent SCT, whilst probably the least used scope in my little scope arsenal, is a pretty handy thing to own. I've not tested any others other than the one I have, so I can confidently say that the Meade LX90 10" ACF is the the lightest, clearest and most impressive and manoeuvrable SCT I have ever taken a look through

Doesn't even come close to clarity of pinpoint stars and such as the refractors I own, but still eats them all alive on plenty of other things.

[russ.will]

I keep coming back to the idea of selling about 3 scopes and getting a c8 or meade 8"

That is basically what I did. I'm guessing at least one of those Skymax in your signature is feeling nervous about that statement, although I'm not sure how different the SCT to Mak Cass viewing experience would be? I suppose the one advantage with the Meade would be the use of 2" EPs.

Russell