86 replies to this topic

[Alrakis]

Hi all!

 

I am currently using a Skywatcher 100ED Pro on a CG5-ASGT. I am really enjoying this telescope and the views that it can deliver. However, as is usual, aperture fever has set in, and I have a few potential options that I am thinking about, but two of them are Celestron 9.25 Edge HD or the Celestron 11 XLT. 

 

Currently I am mostly viewing lunar/planetary, double stars and some of the brighter deep sky objects as well as lunar/planetary imaging. Unfortunately, I don't have a lot of time to get to a dark site to look at the more dim galaxies and know that i need a larger scope to bring them in.

 

So my question is about the difference between Celestron SCTs with the Edge HD optical design vs. the standard (XLT). The price new for these two OTAs are very similar ($2100 for the 9.25 Edge HD vs $1850 for the C11 XLT); so is it worth losing the 1.75" of aperture for the better control of optical aberrations that come with the 9.25 Edge HD. 

 

Thank you in advance for your help.

 

Chris

[J A VOLK]

For the purposes you describe I would go for the C11, aperture rules - center of field views are the same as the Edge and looking through less glass. The off axis view can be well controlled with good eyepiece selection. If you were going to do much prime focus imaging, the Edge would be the better choice.

[jallbery]

Are you planning on buying a new mount?   I think Celestron may have sold a C11 on CG5, but I would think that would be too much scope for the mount.   Even the c9.25 might be pushing it (it's a big increase in weight compared to a c8).

[Patrick]

Hi all!

 

I am currently using a Skywatcher 100ED Pro on a CG5-ASGT. I am really enjoying this telescope and the views that it can deliver. However, as is usual, aperture fever has set in, and I have a few potential options that I am thinking about, but two of them are Celestron 9.25 Edge HD or the Celestron 11 XLT. 

 

Currently I am mostly viewing lunar/planetary, double stars and some of the brighter deep sky objects as well as lunar/planetary imaging. Unfortunately, I don't have a lot of time to get to a dark site to look at the more dim galaxies and know that i need a larger scope to bring them in.

 

So my question is about the difference between Celestron SCTs with the Edge HD optical design vs. the standard (XLT). The price new for these two OTAs are very similar ($2100 for the 9.25 Edge HD vs $1850 for the C11 XLT); so is it worth losing the 1.75" of aperture for the better control of optical aberrations that come with the 9.25 Edge HD. 

 

Thank you in advance for your help.

 

Chris

 

For faint fuzzy observing, aperture is always king.  As far as putting a C11 on an CG5 mount, a friend of mine used one for quite some time for visual observing.  It is pushing the max weight limit and a motor driven focuser might be a good idea, but it can be done.

 

Patrick

[rmollise]

I'd vote for an Edge 800. Maybe the best SCT optics out there in an 8-inches today, and reasonably light. It's what I use and because of this scope's combination of good optics and light weight my C11 stays in her case most of the time.

 

Runner up? Meade ACFs. Excellent scopes, too. In fact, if I had it to do over again, I'd be tempted to buy a Meade 10-inch f/8 instead. An 8-inch is really a better match for me at this stage, however.

 

In this game it's easy to start playing the aperture card, "If an 8 is good, a 10 is better, and a 12 is better than that." That may be true in some sense, but after the newness wears off, most people will find that will use an 8 far more often than a larger telescope. That is one of the things that has made an 8-inch SCT a perineal winner.

Edited by rmollise, 23 July 2016 - 07:31 AM.

[rmollise]

For the purposes you describe I would go for the C11, aperture rules - center of field views are the same as the Edge and looking through less glass. The off axis view can be well controlled with good eyepiece selection. If you were going to do much prime focus imaging, the Edge would be the better choice.

 

The off axis view cannot be controlled by good eyepiece selection. Only a corrective element of some kind will reduce the field curvature and coma inherent in a standard SCT. It's not that bad to me, but some people do not like it.

[junomike]

I have an 8" EdgeHD, C11 (NS11GPS) and C14 (CGE).  I do feel the optics in the EdgeHD are better than those in my other SCT's but Aperture can't be ignored.

I'd get the C11.

 

Mike

[Bill Barlow]

Chris, if weight is not an issue, get the C11.  But a standard C9.25 has a slightly different optical design with a slower primary mirror that usually gives excellent views and impoves a bit from the other celestron standard SCT's..and is lighter than a C11.  I would opt for the standard C9.25 and save some money. 

 

Bill

[Stelios]

I just got an Edge HD8. I've owned two each regular C8's and C9.25's. All were good examples, but the EdgeHD leaves them in the dust when it comes to optical quality, as good an optic as I could've wished for. And this is talking about the "center part" of the view, not the flatter field.

 

However, this mainly will matter for planetary and double-star observation. For deep sky, nothing beats aperture. But you will *not* enjoy deep-sky objects from light-polluted skies anyway. You might be able to *see* them when they're near-invisible in your 4", but you won't enjoy them till you go to a dark site. 

 

In your case, you should consider that you have a CG-5 and apparently plan to simply buy an OTA. The C11 on the CG-5 is marginal, even for visual, whereas the 9.25 will be just fine. This concern, combined with that you usually observe from the city so doubles and planets will still be your main dish, make the 9.25" Edge a better choice. 

[jallbery]

 That is one of the things that has made an 8-inch SCT a perineal winner.

 

While there is no doubt that Rod intended to use the word "perennial" (and was possibly autocorrected), I have to admit that "perineal winner" gave me a chuckle.

[jhayes_tucson]

The image quality of the Edge systems is superb; however, if your main interest is in planetary observation, there won't be any significant difference in image quality between an Edge and a XLT system.  I always recommend getting a bigger scope if you can handle it.  I have a C14 Edge so I think of the C11 as being a very light system but Rod has provided solid advice about portability so think carefully about whether you are willing to move a larger scope.  Larger scopes gather more light and will provide a sharper image than smaller scopes but they need a bigger mount and weight more.  The well corrected field of a XLT will not be as large as the field in an Edge system but you need some pretty high quality eyepieces and a critical eye before the differences really jump out.  One other thing to keep in mind is that the Edge systems hold their value a bit better on the used market than XLT systems--when the time comes to sell it.  For those who want the best or who are doing imaging with a large sensor, the Edge systems win hands down.

 

John

[Cpk133]

The 9.25 xlt has been a goldilocks scope for me.  Not too big, not too small.  It does a superb job on planets and double stars when seeing cooperates.  It's big enough to show star clusters well in my moderately light polluted sky.  It does really well on deep space objects under dark skies.  I've had a number of experienced observers tell me the optics are superb and I'd have to agree.  It rides the AVX class of mount well and that makes the load out a bit easier.  With that said, I'm looking to add a 80 - 100mm refractor for nights when I just want to walk out and observe.  My vote is for 8 edge or the 9.25 xlt.  A lot of bang for the $ with the CG5.

[Arizona-Ken]

I have often looked through my CPC1100 XLT (non Edge) vs a friend's C11 Edge OTA mounted on a CGEM. I found no significant differences visually. However, my friend was into AP and took some great pictures with his OTA. If photography will be important to you, go with the Edge; for visual purposes spend the money on a larger OTA.

 

Arizona Ken

[Daniel Mounsey]

For visual I prefer the standard model non-edge. 

[RickV]

I'd go for a C11 XLT over an Edge C8 or C9.25.

Aperture rules and for planetary (high power) you will only be using the center of the field of view - so in my opinion the C11 XLT is the better choice for performance.

If you want wide field of view (at low power)... I'd go for a short focal length refractor.

LOL!  It's great to give someone else advice... when it's not your own money!

[Alrakis]

 

 That is one of the things that has made an 8-inch SCT a perineal winner.

 

While there is no doubt that Rod intended to use the word "perennial" (and was possibly autocorrected), I have to admit that "perineal winner" gave me a chuckle.

 

ISWYDT

 

That is funny.  

[Alrakis]

For visual I prefer the standard model non-edge. 

 

That is interesting. I have not heard that the Edge HD is not as good visually as the standard model. Is this a on-off issue, or is it true for because of the optical design. I would think (since I don't know any better) that all things being equal, that if imaging was a big concern of someone, that the ability to use the hyperstar F/2 at a prime focus would be more important than imaging at a cassegrain focus at either F/7 or F/10. Is this an incorrect assumption.

 

Chris

[junomike]

For visual I prefer the standard model non-edge. 

Daniel, can you elaborate on why?

 

Mike

[Daniel Mounsey]

For the purposes you describe I would go for the C11, aperture rules - center of field views are the same as the Edge and looking through less glass. The off axis view can be well controlled with good eyepiece selection. If you were going to do much prime focus imaging, the Edge would be the better choice.

 

[Daniel Mounsey]

 

For the purposes you describe I would go for the C11, aperture rules - center of field views are the same as the Edge and looking through less glass. The off axis view can be well controlled with good eyepiece selection. If you were going to do much prime focus imaging, the Edge would be the better choice.

 

The off axis view cannot be controlled by good eyepiece selection. Only a corrective element of some kind will reduce the field curvature and coma inherent in a standard SCT. It's not that bad to me, but some people do not like it.

 

 

 

In my opinion, based on the comparisons I've made, it depends on what aberrations affect the observer the most. Eyepiece selection has a profound impact on image quality one sees. Don't forget that with the Edge, the camera is relying completely on the optical tube to flatten the FOV. Visual observation is an entirely different animal and observers shouldn't just assume that carries precisely the same way into the visual world. The observers own eyes and eyepiece selection can have a profound impact on ones perception of the image. 

 

Heck, there's observers who swear they see field curvature in one eyepiece vs others and others will say just the opposite. Also, collimation on the Edge is extremely tight because of the critical distance the secondary resides from the corrector. I've looked through several samples of the Edge and I still can't figure out what all the hype is about when used "visually". Photographically I can understand, but visually, not quite. Even scope sample of all brands have variances, even if it's the exact same model. 

 

Just to put this into perspective, I test various samples of cass's with Darren Thibodeau who's a contributor to my website. We observe with numerous samples which we check. Just the other night I ran into sample of a 10" ACF that shocked me. It stood up to premium scopes I've tested. The sample was so staggering good that I told my friend not to let it go. Not all samples test exactly the same if you guys want to be that nit-picky about it. 

 

That's not neccesarily to imply that all ACF's are better. I'm merely trying to say that not all these scopes test exactly alike if you really want to get down to it. I'm not trying to be mean, but when people continually assume that Edge's are always better than normal SCT's, that to me is a red flag. It's just not that simple. 

 

Prime example is the Takahashi FSQ106 EDX. For imaging it produces a flat field. With a 35 Panoptic visually, it does not produce perfect pinpoints out to the edge of field. Take an NP101 and it produces pinpoint images with a 35 Panoptic out to the edge because the telescope was designed to be used with Televue's own eyepieces. 

 

These are complicated optical systems. You can't just assume that because an astrograph is flat field with a camera, that it automatically means it's going to carry over to eyepieces. Sorry to rain on the Edge parade, but I just can't agree with all these assumptions. 

Edited by Daniel Mounsey, 25 July 2016 - 10:28 PM.

[J A VOLK]

For the purposes you describe I would go for the C11, aperture rules - center of field views are the same as the Edge and looking through less glass. The off axis view can be well controlled with good eyepiece selection. If you were going to do much prime focus imaging, the Edge would be the better choice.

 
The off axis view cannot be controlled by good eyepiece selection. Only a corrective element of some kind will reduce the field curvature and coma inherent in a standard SCT. It's not that bad to me, but some people do not like it.

improved, made acceptable for most might be better stated. For example the hard to find TMB 40mm Paragon (68 deg AFOV!) gives very good (not perfect) edge performance on a classic f/10 - f/11 SCT - far superior to 41mm Panoptic and many others in this category I tried.

Edited by J A VOLK, 25 July 2016 - 11:25 PM.

[Stelios]

 Sorry to rain on the Edge parade, but I just can't agree with all these assumptions. 

 

 

Rain away, but looking through the eyepiece of mine is all the umbrella I need 

 

I know YMMV, but I've owned 5 SCT's and this is by far the best in both build and optical quality. Admittedly the most recent one was a 2004 9.25" so perhaps today optics overall are much better. Still, I'm very happy with mine.

[stevecoe]

Hello Stelios, et al;

 

Well, the 9.25" I have is the one I purchased from Stelios about a year ago, maybe a little more.  I am very happy with the views in that tube assembly and I have it riding on my CGEM, which I bought from Starizona about 3 years ago.  The only imaging I do is piggybacking with a DSLR and camera lenses.

 

I have just recently turned 67 years old and I find that the 9.25 is all that I want to lift onto the mount.  More weight would be too much of a problem for me.  I do travel to dark Arizona skies and I find that I really enjoy the contrast and sharpness of this telescope.  I can highly recommend it.

 

Clear skies;

Steve Coe

 

[SandyHouTex]

 

For the purposes you describe I would go for the C11, aperture rules - center of field views are the same as the Edge and looking through less glass. The off axis view can be well controlled with good eyepiece selection. If you were going to do much prime focus imaging, the Edge would be the better choice.

 

The off axis view cannot be controlled by good eyepiece selection. Only a corrective element of some kind will reduce the field curvature and coma inherent in a standard SCT. It's not that bad to me, but some people do not like it.

 

Eyepieces can be used to control abberations.  As the focal length of the eyepiece gets shorter, the field of view gets smaller.  Field curvature and coma are dependent on how far you are from the center of the field.

[Daniel Mounsey]

 My favorite 50mm class eyepiece in the world is the original Celestron 50mm Axiom from Japan. I've compared it to every other 50mm class eyepiece and in my opinion it's the best one ever made. Once in a while you can find one floating around on Astromart for about $250. But when I tried it with the Edge scopes, I noticed that there were more visible aberration around the periphery than with a standard SCT while using it. Someone would probably have to ask one of the optical engineers at Celestron, but I think that eyepiece was designed to be used with SCT's. 

 

Also, when doing critical planetary observation, the  observer should first check the spherical correction of the sample under excellent seeing in any instrument by using various eyepieces. Since eyepieces and prism diagonals can alter spherical correction, the best thing is to match the eyepieces to the system. I wouldn't just assume one factor solves everything in a visual image train. Also when relying on passive cooling, there's a difference between the way the two telescopes behave.