Dan F.
member
Reged: 07/05/10
Loc: Kalamazoo, MI
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EdgeHD or no?
#5265352 - 06/10/12 09:06 PM
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Just wondering what the differences are between Celestron's EdgeHD series scopes and the standard XLT units. I realize there's a second mirror lock (does it matter if I'm going to use a crayford?...) and vents, but beyond that I'm not too sure.
Right now I'm looking to do visual, but imaging won't be too far off. Nothing too fancy. An 8" EdgeHD is a good $800 used, whereas I can pick up a standard OTA for half that (if not less). With the standard tube I'd probably CF and flock it and add vents and handles.
What about the use of a Crayford focuser vs. an upgraded two speed Micro Starlight? Personally I like the idea of a Crayford because the primary can remained locked, but then again what do I know?
Daniel
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JMW
scholastic sledgehammer
Reged: 02/11/07
Loc: Nevada
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Re: EdgeHD or no?
[Re: Dan F.]
#5265367 - 06/10/12 09:37 PM
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Get the edge. Flatter field, vents, better scope for visual and imaging.
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titanio
sage
Reged: 02/15/09
Loc: Alicante, Spain
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Re: EdgeHD or no?
[Re: JMW]
#5265389 - 06/10/12 10:00 PM
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Yes I agree, the EdgeHD has been a suprise for me. As for the use of a Crayford focuser vs. an upgraded two speed Micro Starlight I prefer the two speed Micro Starlight. Toni
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Dan F.
member
Reged: 07/05/10
Loc: Kalamazoo, MI
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Re: EdgeHD or no?
[Re: titanio]
#5265446 - 06/10/12 10:38 PM
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Hmm...what's interesting, though, is that I very much like the performance - visual only - of the NexStar 8 I've been using for the past few months. Appears to be flat all around.
Would a Crayford work fine, though? Wouldn't that get around the issue of single vs dual mirror locks and play in the mirror?
Vents can be easily added to a non-vented OTA, either in the rear or on the tube itself.
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AFAdrenaline
sage
Reged: 12/08/10
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Re: EdgeHD or no?
[Re: Dan F.]
#5265526 - 06/10/12 11:19 PM
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I haven't used the standard SCT model but I love my C11HD scope. If you interested in possibly going the imaging route with it later, I'd definitely recommend EdgeHD. It's also setup hyperstar, which it certainly a neat capability if that is something you are interested in. The optics are fantastic. The only serious problem I see with it is that for best results, you need to use the matching accessories (focal reducer, etc) which can be pricey. In my overzealous first telescope purchase I jumped in head first w/ the C11HD but I can't say I remotely regret that decision at all.
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skyjim
Carpal Tunnel
Reged: 01/13/07
Loc: Long Island, NY
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Re: EdgeHD or no?
[Re: Dan F.]
#5265535 - 06/10/12 11:25 PM
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I have owned in the past 4 different SCT's, 8 MCT's, 2 macnewts and now the C8HD, the optics and the mechanics of the HD scope has been the best I have seen on any compound scope. The extra money is well spent but I would look at a new one not a used one but thats me, if someone gets one new and fiddles with the focuser without un locking the mirror locks it will cause the focuser to have focus shift. The sample 8HD I have has none, rock steady at 300X and smooth. The optics are outstanding, worth every penny.
Jim
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korborh
professor emeritus
Reged: 01/29/11
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Re: EdgeHD or no?
[Re: Dan F.]
#5265620 - 06/11/12 12:46 AM
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Get the EdgeHD. Its a great scope for visual and imaging.
I have the C11 EdgeHD and gives amazing images.
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giulianb
member
Reged: 05/21/08
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Re: EdgeHD or no?
[Re: korborh]
#5265702 - 06/11/12 02:47 AM
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Edge hd, my c8 is optically excellent.
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cam1936
sage
Reged: 08/01/08
Loc: Alberta, Canada
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Re: EdgeHD or no?
[Re: giulianb]
#5265869 - 06/11/12 08:35 AM
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What exactly is different about the HD scopes other than vents and the focuser? Is it simply the corrector, or is there something else in the optical train?
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Eddgie
Postmaster
Reged: 02/01/06
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Re: EdgeHD or no?
[Re: Dan F.]
#5265877 - 06/11/12 08:41 AM
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Well, if you already have an 8" inch SCT, then the answer is obvious. Buy your camera and try imageing with it.
If you like the result, then you are good to go.
And if not, you can sell the current scope and try an EdgeHD.
Oh, I think the EdgeHD is a far better off-axis performer than the standard SCT, but that is not to say that everyone should rush out and buy one. You sound happy with the performance of the standard model, and depending on the camera and targets, it may work fine for you. After all, people have been imageing with C8s for 50 years.
But for modern wide field cameras and eyepeices, the design shows its age.
Again though, why not try it first to see? If you are happy with the result, then that is all that matters.
And whatever accessories you get(with the exception of a standard focal reducer) can be moved over to the new OTA if you later decide to upgrade to an EdgeHD.
So to me, I don't see this as an either/or at this point. More of a "Maybe Later."
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Eddgie
Postmaster
Reged: 02/01/06
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Re: EdgeHD or no?
[Re: Dan F.]
#5265889 - 06/11/12 08:48 AM
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Would a Crayford work fine, though? Wouldn't that get around the issue of single vs dual mirror locks and play in the mirror?
A crayford may introduce vignetting if used with a focal reducer.
The mirror locks on the EdgeHD lock the mirror in place to keep it from shifting as the scope changes orientation. A Crayford will not prevent this.
During long exposures, as the scope changes angle to the sky, the mirror carrier (the tube that holds the mirror and slides on the baffle) can shift slightly.
The EdgeHD has two rods attached to the rear of the mirror carrier. These rods are clamped into place so that even as the scope changes attitude, the mirror itself can't move.
And of course you can add vents. You can put louvers on the hood of a 6 cylinder Mustang, but that won't turn it into a Cobra. Modifying the C8, unless done by someone that really knows how to machine (and maybe that is you) could cost more than the difference between what you could sell your scope for and buy a new one.
I am not trying to talk you into getting an EdgeHD. Actually, I think you should get your camera and try imageing with your existing scope first before you do any modifications. If you don't like it, you can then just sell and upgrade.
And if you are happy, then cut away!
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jrbarnett
Eyepiece Hooligan
Reged: 02/28/06
Loc: Petaluma, CA
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Re: EdgeHD or no?
[Re: Dan F.]
#5266272 - 06/11/12 12:49 PM
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http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/5222156/page/0/view/collapsed/sb/5/o/all/fpart/1
I asked the same question a while back.
I ended up getting a new standard C8 XLT OTA with Fastar secondary for $799.
Factors that guided my decision were (a) considerable cost savings ($800 vs. $1300), ability to use Lymax cat cooler with non-Edge scope (the Edge has lenses in its baffle tube), (c) the fact that I don't plan to image with the scope and (d) based on past SCT ownership already have many accessories including the FF/FR for the standard SCT.
Depending on how you plan on using the scope, you could come out in a different place on the analysis. As for the Feathertouch microfocuser versus a Crayford, I've used both and have the Feathertouch on my current CPC-1100. For me it comes down to whether you got the short end of the stick in the mirror-shift lottery with your OTA. If you luck out and get a mirror with near-zero-shif during focusing, the Feathertouch is outstanding. If, however, you end up with a shifty mirrored unit, the Feathertouch won't fix that and if it bugs you, a Crayford is the better choice. Th eCrayford, however, adds system focal length and weight to the rear of the OTA, so if that matters to you, you may want to skip it.
Also, if you want more granular focusing than the stock focuser provides, but are interested in skipping the expense of the Feathertouch or a Crayford, this Delrin knob works well:
http://www.scopestuff.com/ss_foc6.htm
Regards,
Jim
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Alph
Pooh-Bah
Reged: 11/23/06
Loc: Melmac
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Re: EdgeHD or no?
[Re: cam1936]
#5266452 - 06/11/12 02:35 PM
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Quote:
What exactly is different about the HD scopes other than vents and the focuser? Is it simply the corrector, or is there something else in the optical train?
Just the corrector and some tweaks to the design. The secondary mirror has a slightly different curvature radius and it is located closer to the primary mirror.
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MrJones
Pooh-Bah
Reged: 09/15/10
Loc: Indiana
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Re: EdgeHD or no?
[Re: Alph]
#5266504 - 06/11/12 03:00 PM
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I sure like the C8 EdgHD for visual but what can you use for a focal reducer? Hyperstar seems expensive for a C8 and there is not an offical EdgeHD reducer for the C8. And the C11 and C14 ones are $580!
Also for one more data point, I have a standard C9.25 and it has no focus shift.
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freestar8n
Carpal Tunnel
Reged: 10/12/07
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Re: EdgeHD or no?
[Re: cam1936]
#5266609 - 06/11/12 03:51 PM
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Quote:
What exactly is different about the HD scopes other than vents and the focuser? Is it simply the corrector, or is there something else in the optical train?
Just to be clear - in an SCT the "corrector" is the big piece of glass in the front. In the Edge there is a set of additional "corrector lenses" near the back of the 'scope. The system is designed as a unit, so it's not like the lenses were just added to a normal sct - the whole thing was designed to work together optimally to provide a flat and corrected field.
The exact optical design is described in some detail in the new book, "Telescopes, Eyepieces, Astrographs" from Willmann-Bell - so there is less need for speculation about how it differs from a normal sct.
In order to flatten the field of a system that has a curved field, you need to add additional lenses or curved mirrors to compensate for the curvature. You can't fix field curvature by a little tweak to one of the surfaces. So - if you don't see additional field flattening optics - you know it won't have a flat field.
Frank
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skyjim
Carpal Tunnel
Reged: 01/13/07
Loc: Long Island, NY
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Re: EdgeHD or no?
[Re: freestar8n]
#5266828 - 06/11/12 05:48 PM
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When I called Celestron before I purchased my C8HD they said that it was not as simple as taking the standard optics and place the correcting lens in the ota, that there were changes in the secondary, also the secondary housing and each set of optics had to be matched, the secondary housing had to be optically centered onto the corrector before the system was even checked then the correcting lens was installed, position adjucted then final testing on the whole ota was done. The bearing race is different for the focusing system on the HD scopes as well so for all that think they take a C8 and plug in a few tweeke gotta really be dreaming here, they came out with these scopes to produce the best visual or AP style sct around and they are QCing from what I am told every scope.
Is the Edge scope worth it IMO Hell Yes!
Jim
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swsantos
super member
Reged: 09/29/05
Loc: Rhode Island
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Re: EdgeHD or no?
[Re: skyjim]
#5267367 - 06/12/12 12:26 AM
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First light last night with 21mm Ethos and Edge 8HD. Pinpoint stars to the edge.
Edge HD yes!
Steve
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MHamburg
professor emeritus
Reged: 06/21/06
Loc: Brooklyn, NY/Berkshires, MA
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Re: EdgeHD or no?
[Re: swsantos]
#5269163 - 06/13/12 08:32 AM
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If any SCT approaches the performance of a refractor, my Edge 11HD is as close as it gets!!
Michael
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mistyridge
Carpal Tunnel
Reged: 10/28/05
Loc: Loomis, CA
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Re: EdgeHD or no?
[Re: MHamburg]
#5270623 - 06/14/12 02:47 AM
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I have to agree. Last night I put my new Edge C8HD through the paces. Saturn.. refractor like perfomance the same for Mars. I tried my 31mm Nagler which gave me pin point stars to the edge of the 1.2 degree FOV. Collimation right out out the box was dead on. A crude star test was perfect best I could tell. You would never know you were looking through a SCT. 
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skyjim
Carpal Tunnel
Reged: 01/13/07
Loc: Long Island, NY
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Re: EdgeHD or no?
[Re: mistyridge]
#5270782 - 06/14/12 08:10 AM
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Man you guys are right on the money, Mike mine too was collimated outa the box, hard to belive cause I didnt expect that but evry time I have the scope out I gotta pinch myself, the veiws are like a long focus APO(F8-F9ish). All my WF ep's I now really enjoy, no feild curvature when observing lunar at lower powers and the scope is soo light and portable. Best star test I have seen outa any compound scope in a while. For two years I had an very good 7" MCT but if I would have tryed one of these scopes first I would have switched. Is the HD scope worth the extra cash, hell yes!
I think JB didnt want to get an 8HD cause he didnt want to give his beloved TEC 140 any competition. I know someone who has a AP130 and a HD that will pull far ahead on most nights, only on poor seeing conditions were smaller aperture rulls in some cases. I find even on those nights you just dont push the power up but when the seeing is good watchout this puppy cranks.
Jim
Edited by skyjim (06/14/12 08:17 AM)
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