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C11 SGT XLT vs 8" Edge HD and C9.25 SGT XLT vs C11 SGT XLT


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Hey guys,

Thanks for your first round of help. As a result I have decided to go for a CG-5 EQ mount over an alt/az.

I am now considering the following SCT OTA's (price approx inc. mount):

- 9.25" Celestron C9.25-SGT XLT - £1300

- 11" Celestron C11-SGT XLT - £1700

- 8" Celestron Edge HD - £1300

But I have two questions I hope you can help with:

1:

Given the cost similarities is it worth losing 3" of apature to get the 'more advanced' 8" Edge HD instead of the 11" SGT XLT 'standard' scope? Are the optics in an 8" Edge HD really that much better than a 11" SGT XLT?

For reference, I will mostly be doing visual work on DSO's, but hope to get into astrophotography in a year or two. Starting with a DSLR and maybe moving upto an AP dedicated CCD camera.

Does anyone have any thoughts these two OTA's? Better yet, does anyone have any practical experience with the 11" SGT XLT and/or the 8" Edge HD that can compare the two scopes?

I know on paper the 11" scope should 'win' hands down, but surely there is a reason why the scopes are in a similar price range? Are the advantages purely directed at the Edge HD being a 'best in breed' OTA for astrophotography? Or can it genuinely challenge the C11 for visual performance too?

2:

I would like to do a slightly more straight forward comparison of the C9.25 SGT XLT against its big brother, the C11 SGT XLT for visual work only.

Does anyone have any practical experience of the two - how much clearer/brighter/bigger will DSO's appear to be in the 11"?

I only ask because while my budget extends to the C11, I want to be satisfied that its 'on paper' superiority over the C9.25 translates into a noticeable improvement in visual performance. (I am not worried about how these two stack up for AP).

Again, does anyone have any practical experience of the C9.25 and/or the C11 that can offer a view or a comparison of the two?

Once again, many thanks in advance ;)

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http://www.cloudynights.com/item.php?item_id=1464hi. this is just my pennys worth never looked through the 8 or 11" but a lot of peeps not just on here reckon the 9.25 is the best of the bunch the jewel in the crown. i have owned my scope now for just over a year and can honestly say i cant fault it at all amazing on planets and dso,s, im sure some one will put up a fight on this though :smiley: but read this review see what you think
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I would have a problem with coma shown by stars in the 9.25 and 11 inch models you mention. I have a bag full of Televue eyepieces which I would have thought would not correct coma. As such these would for me be a waste of money. I have 12 inch Meade HD Edge version of the scope which I am sure is very much the same if not exactly the same. I thing the Celestron variant of the system is too expensive and Meade is bigger. The downside of it is the mount. I would try and buy the 8 or 10 inch Meade tube instead of the celestron, you could still put it on the Celestron mount and if you went for the later you would have a bigger scope.

But I am lead to believe the 9.25 celsestron is the better of the range though I have never used one.

Alan.

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I have the "vanilla" C8 OTA, and coma is not much of a problem visually for me, even with the 31T5. I find that the magnification of EPs wide enough for coma to set in, is so low that the coma is not really easy to spot. In a fast Newtonian it is generally worse, in my experience. The C9.25 with its slower primary should be better than my C8. Photographically, the coma is a bigger problem, but for planets it is not an issue, and for DSOs you can get a focal reducer/coma corrector for the regular C8 to C14 (still not the ideal set up for DSO imaging). For Edge-HDs I have yet to see a remotely affordable focal reducer, and DSO imaging at F/10 is only for the very patient.

The CG5 EQ mount is not strong enough in my opinion for the C11 OTA (quite a few manufacturers sell scopes seriously under-mounted). You need a CGEM(DX) for the C11 (the Meade OTAs are heavier, so need the CGEM for the 10"). The CG5 may hold the C9.25, and certainly the C8. Probably the C9.25 is the best choice.

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Thanks for corecting my error, I thought a 10in Meade would be OK on such a mount, that being the case is the 9.25 Celestron not sailing close to the wind if he wanted the mount for imaging.

You are dead right with the seling of mounts too small for the scopes. I bought my Mac Newt 190mm with a HEQ5 Pro, the catalogue had the picture of the two on the front cover together. I , not being able to visit a showroom with them in just ordered the two. When I joined the site here they were bending backward to tell me the mount was too small. Pays to ask.

Alan.

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Hi guys - thanks for the posts. Think i should add something that I forgot to put in:

I accept the CG-5 mount is not ideal for AP - I intend to upgrade to a better mount in the future if I really get into AP - but for now my budget doesn't extend that far and I can't justify the additional price.

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I agree with Mike only because I don't know any better, I have always read that the 9.25 was the best one to have, I almost got that one myself, it was only because at the time there was no Celestron dealer in Bulgaria. There was a Meade dealer so I got a Meade. I am sure you will get many many hours of enjoyment from it. I don't know how much you have to play with for buying a mount but the iptron 45 looks a super mount and it is not silly money, this would do you for CCD work I am sure. I might get one myself.

Alan.

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I have the 11 and 8 in reverse (C8XLT and 11HD) but I've not had them back to back, although I would like to at some point. The Edge HD gives you a flatter field which is probably more important for imaging. I've had only one brief look through my ES82 30mm with the 8 and suspect I was getting a small amount of something at the edge, but the majority of the view was good.

The mirror of the 11 (hd or not) is almost twice the area of the 8 and about 40% more than the 9.25, so brighter... bigger is better! BIG BUT coming... there are physical points to consider... the size and weight of the 9.25 isn't much less than the 11 and the 11 is a beast. I feel more comfortble with the NEQ6 for the 11 (also big and heavy though :( ) The 8 feels tiny by comparison!

There's also the reducer point... the reducer for the Edge scopes sell for $5-600 in the US (don know UK price), but a fraction of that for the XLT models. The Celestron reducer/corrector not only gives you a wider field but supposedly flattens a bit (not tried one)

I'm not convinced that the 9.25 is particularly special, maybe the limits of its capabilities aren't so inhibited by the weather as much?

For DSO imaging, you're going to want a small refractor - but the same mount that can cope with a C11 should do a decent job with a small refractor too :)

Whichever way you go, you can always upgrade :eek:

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For DS imaging these telescopes are a triumph of marketing over common sense. The Edge optics are superbly corrected for flatness of field, coma etc. This is most unlikely to matter if you are a visual observer. It is even less likely to matter if you are an astrophotographer because the slow focal ratio makes the entire thing unsatisfactory. If you are using a DSLR which, being uncooled, cannot do long exposures (30 mins), then the slow F ratio is totally inappropriate. In a nutshell this is why so few people use them. You can get great results with them if, with a CCD (possibly binned 2X2) you take a very long time to capture your data and can do long, long sub exposures. There is a focal reducer (indeed there are two) but when I last looked only the Lepus quoted an image circle and it was very small. The very expensive Celestron one did not quote an image circle. Why? Too embarrassing?

These are telescopes for very experienced imagers who know what they can and cannot do and are prepared to work around their shortcomings in order to image certain small targets on special occasions when the seeing allows. In these circumstances the excellent optics can deliver a great result but the circumstances are very specialized. If you are not fully cognizant with astrophotography I would strongly advise you to look in an entirely different direction. Orion Optics do Optimized Dall Kirkhams at F6.8 which is a seriously workable F ratio. F10 just isn't. It's crazy. The C14 is F11, isn' it? That's even worse.

The more imaging I do the more I want fast F ratios.

Olly

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The good thing about the C series is the fact that IF you are imaging planetary bodies then your exposure times will be far less important, and as a result so will accuracy. The majority of people who have done their research, or spoken to experienced APs know that the large f ratio is not for long exposure DSO imaging. Where these scopes do excel is with planetary imaging and observation. It really all depends on your target of choice. If you want to image DSO then go for a frac; imaging planets - the long FL will suit you to the ground.

I personally believe that there is too much emphasis on DSO imaging, and advice seems to swing towards that direction far too often. The planets are dynamic and ever changing, and this can be a pleasure to photograph also.

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Hey guys, thanks so much for all the help. Its clear that the CG-5 is not suited to the C11 and as the Edge HD isn't going to offer me more (visually) than the C9.25, I am going to preserve my cash and get the C9.25+CG5.

As I am totally new to astronomy and this will be my first scope I'll be quite happy for now so long as it will offer enjoy good visuals on the moon, planets and DSO's. It seems that minus a little wobble the C9.25 and CG-5 it will do the business.

For me AP is an aspiration for the future once I have more practical experience (and money) and i will certainly upgrade the mount when I get into AP based on these comments. So long as the C9.25 will offer me good visuals and maybe get me started on AP then I'm a happy chappy :)

It seems the C9.25 will be a good place to start from. Again thanks so much for such good advice :)

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Can I just clarify that I personally regard the typical EQ6 comfort zone for DS imaging to be about a metre of focal length but people do get them to track at much longer FLs. Tim recently posted a stunning Eagle at native FL with a C11 on an NEQ6. I can only say that my EQ sixes would not do that, but some do. I'm an 'astronomy provider' so that means I need stuff that works and works 'Now, tonight and straight away!' I cannot spend an hour fiddling with the mount while guests wait for me to get it sorted out and their astronomy holiday ticks by.

My bafflement as to what the Edge scopes are all about is simply this; you don't need the Edge optics for visual or planetary imaging and if you want a deep sky astrograph with Edge quality optics and flat field you don't want it to be F10. F8 would be a general minimum for most people and I'd go for F7 in a large reflector. No slower.

Hyperstar, yes. It does have quite a few issues as a system and isn't for everyone but it does make sense. That's easy to see. If you're up for the fine tuning then go for it.

Olly

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I agree that DSO imaging with a SCT is tricky - I've tried it myself with my C11 at native focal length and it isn't easy. However, there comes a time when you yearn to image something different. This means turning away from the normal large fuzzies that fill the forums and start looking at some galaxies. These are mostly small, very small. I just can't get excited about an image having a 60' x 40' area with a galaxy in the middle measuring 3' x 40". This means a longer focal length is required to reel in that galaxy. People are always advised to get a "fast refractor" because it means that you need "less exposure time". You only need less exposure time because you're squashing the same amount of light into a smaller area. Then they come back asking how they can make things "bigger". I think too much emphasis is placed on the f-ratio. What's more important is the focal length and matching that with your camera AND the target you're after. True, starting with a fast system gets you going, but sooner or later you need more focal length. If you can get that AND a larger aperture at the same time (and hence keeping the f-ration manageable) then all well and good but not many can afford a mount capable of holding (and guiding) such a beast.

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