Dave's Astronomy    News Posting: 2013-09-03
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New EdgeHD Telescope
First Images from the Celestron 11" EdgeHD Telescope
2013-09-03

Recently I obtained a new Celestron 11" EdgeHD telescope. It is by far my biggest telescope to date and has a 2800mm focal length and a little over 279mm of aperture. The telescope a Schmidt-Cassegrain reflector and features a built in field flattener along with a number of mechanical changes and other advancements over the previous generation of Celestron SCT's.

Below are the first images I've taken so far with this telescope.

M56 - Globular Cluster in Lyra
First image from the 11 inch
First image taken from outside the city
This image of M56 was the first image taken from outside the city.

Since this image was only intended to be a test of the off-axis guider I didn't bother taking dark farmes. As a result the image came out noisy and there are some other issues like color balance as well. Oh well, I did a enough cleanup to make it presentable and posted it here anyway.

In spite of some image quality problems, the stars are mostly bright and round so as a first test, I was fairly happy with the result.


NGC6946 - The Fireworks Galaxy
First image from the 11 inch
First galaxy image from the new scope
The Fireworks Galaxy was the first long exposure test.

Capturing the raw images took a little over two hours. Out of that came 84 minutes of usable light frames and 12 minutes of dark frame. With the darks in the stack, the end result was a lot less noisy than M56 above.

Our view of NGC6946 is somewhat obscured by dust in our galaxy which apparently makes a really clear picture pretty much impossible. Nonetheless, I think it came out all right as the first galaxy image taken with the new scope.


For those interested in my initial impression of the new scope, I've included the article below.


First images using the new scope

The images were taken the morning of September 2, 2013 at the Blackfoot Staging Area outside of Edmonton, Alberta.

I'm no expert on sky conditions, but I would say that the seeing was OK but not great. On the other hand there were no clouds and no moon. Around 3am, the temperature was reported to be 9°C. Basically it was about as average as it gets for early September out at Blackfoot. If anything, the pictures taken in these conditions should provide me with a good baseline for future imaging sessions.

Besides the new EdgeHD 11, the rest of the gear included:

  • Skywatcher NEQ6 Mount
  • Celestron Off-Axis Guider
  • Orion Starshoot Autoguider
  • Canon 60Da DSLR Camera

    PHD was used to do the guiding and the images were captured with BackyardEOS. The stacking was done in DeepSkyStacker and the final cleanup work was done with Corel PhotoPaint. The M56 image consists of 6 frames at ISO 800, 2 minutes each for a total of 12 minutes. NGC6946 is composed of 21 exposures, ISO 800, 4 minutes each, for a total of 84 minutes.

    The M56 image was both noisy and had color balance issues. The noise came from a lack of dark frames and the color was probably due to my exposure time and ISO settings. It took a fair bit of post-processing just to get it to what you see here. After strugggling for a few hours it came down to clarity -vs- color. I chose clarity and now it looks pretty clear but it's also kind of orange. Such is life.

    The Fireworks Galaxy was easier. I did spend a lot of time post-processing until I learned from Wikipedia that our view of that particular galaxy is actually obscured by dust. After that I gave up on the quest for the razor sharp look and just got the color balanced and the thing looking reasonably focused. Compared to other images of this galaxy I found the net, this one's not too bad so I was quite satisfied for the first attempt at a galaxy imaging.

    Click here for the full size image of M56 and click here for the full size image of NGC6946.


    Looking through the EdgeHD

    The night before taking the above images, I was also out at Blackfoot, but only for looking through the new toy. For someone used to a 4 inch refractor, the new scope proved to be quite stunning to look through. M13 resolved into a big bright ball with numerous glittering stars in and around it. M27 and M57 were similarily big and bright and I and several other people who came out that night spent a lot of time staring at these two.

    Thanks to suggestions from the peanut gallery, we also saw Uranus and Neptune. Uranus was quite clear and showed up as flat blue featureless disk. Neptune proved to be a small bright bluish spot that was obviously not a star. We looked at a good number of other objects as well, mostly Messier objects from the EQ6 guided tour function. For the most part, everything showed up clear and bright. It seems that for visual use, only the faintest objects can elude this scope.

    My earlier visual tests from the city were rewarding as well. Under a full moon, not far from downtown Edmonton, I was able to observe the central star in the Cat's Eye Nebula. This was not something I could do before even under ideal conditions. The Ring Nebula was also big and bright, the best I have ever seen from the backyard. Since I was mostly fiddling with the OAG at the time, I didn't really take a good look at much else but what I did see was pretty good considering the conditions.

    Since the moon was out when the scope arrived, I also took the opportunity to get a few lunar looks as it passed between the houses. Outstanding. I have never seen the moon at this level of detail before and it really impressed me. Even through thin clouds, I could see craters within craters within craters. I saw a long trench that looked like it came from a from a seriously large asteroid that glanced off the surface. I could see all kinds of shadows almost everywhere on the surface. This was just all too cool and I wanted to get the camera but I couldn't pull myself from the eyepiece. Then the moon disappeared for good under the clouds and it was all over until next month.

    Overall, I am quite happy with the visual performance of this telescope. As advertised, the stars are indeed pinpoint out to the edge of the field, at least as far as I could tell. The camera seem to back this up as well. A guided test of a star field near Sadr gave me nearly perfect circles right up to the edge of the image. For most of the Messier objects the view is big and bright. The overall clarity and image quality seems to be pretty good too. I'd say that the view through the eyepiece is a lot like the view through a 4 inch APO refractor but at 5x the magnification.


    Eyepieces and the diagonal

    The viewing so far is mostly through the 23mm Luminos eyepiece that came with the scope and a Televue 14mm Delos from my kit. For objects that warrant a real close look, Baader Hyperion 5mm and 8mm eyepieces are also in the kit. An Antares 12.5mm eyepiece with an illuminated reticule is used for alignment. Overall it's a pretty fair range and every eyepiece came to focus and worked properly in in the new scope.

    To my untrained eye, the views through the Luminos and Delos appear to be generally excellent. The Luminos shows a wide field that is clear and bright and the Delos comes through with contrasty, detailed close-ups. The Hyperions also work well but they can be difficult to focus. The slightest touch of the focusing knob causes vibrations that are annoyingly persistent at the higher magnifications provided by these two eyepieces. However, once focused, the view is still pretty good and for splitting really tight double stars, these two do the job nicely.

    Besides the 23mm Luminos, Celestron also supplies the EdgeHD series scopes with a 2" mirror diagonal. The diagonal works perfectly well but instead of a brass compression ring it uses set screws to hold the eyepiece. My other diagonals have the compression ring and I found that I prefer that to the set screws in the supplied diagonal.

    A nice thing about the supplied diagonal is that it has a removable nosepiece and Celestron included a standard 2" smooth-bore nosepiece in the package. This allows you to use the diagonal in other scopes that have a standard 2" focuser. It also means that if you install a 2" adapter like the Baader click-lock on the OTA you can still use the supplied diagonal.


    Other features on the EdgeHD series

    As mentioned above, the telescope has a built in field flattener. This corrects the curved field that comes off the primary mirror and presents a flat focal plane to the camera or eyeball. As far as I can tell it works perfectly. The stars are round and sharp right out to the edge of the 82° 23mm eyepiece supplied with the tube. Same with the view from the DSLR. My test images show round circles all the way to the image borders. I don't have anything really wide to try on it but so far so good.

    The mirror has locking clutches to prevent mirror shift while imaging. For visual use I left them loose as I was constantly changing eyepieces and refocusing. I did notice that slewing back and forth did occasionally cause a slight loss of focus, presumably due to the mirror moving while in motion. Locking the mirror did seem to help but I didn't do a real test so I can't say for sure what was going on there.

    I did lock the mirror for imaging and it seems to have worked. Most of the raw images came out quite good, Any issues with the images likely had more to do with guiding, imprecise focus and my camera settings than anything in the mirror itself.

    The tube also has vents to allow the mirror to cool down more quickly. I couldn't actually tell if they made any difference or not. I will assume that this is a good thing and it shows that the vents do indeed work and you can basically start using the thing right away.

    The supplied finderscope is a 9x50 so its fairly big and bright as far as finderscopes go. It has a spring loaded set screw system so it's easy to adjust and it so far it holds the adjustment pretty well between setups and teardowns. It did have a tendancy to dew up though, a small dew shield is probably all it needs. Other than that it works just fine and I don't see a need to upgrade it anytime soon.


    Hauling it around and mounting it

    Well, first of all it is pretty heavy. The OTA alone is around 30lbs and fully loaded with the guider, cameras and other bits it gets up around 35 to 37 pounds. The posted limit for the Sky-Watcher NEQ6 is something like 40 pounds so the 11 inch Edge and accessories are about as much as you would want to carry on this mount.

    To be able to balance the telescope on the mount I had to add an additional counterweight. There are now three counterweights for a total of 33lbs. The weights sit right at the end of the counterweight bar so piling on any more gear will require yet another counterweight. Realistically, it's full and I don't plan to add anything else.

    The mount seems to have no issues carrying the load. When full speed slewing, the motors are a bit louder than when it carries my lighter refractor but otherwise it's business as usual. The only real issue is loading and unloading the OTA from the mount. For this telescope I found that I like the tripod fairly high up to distribute the weight further out. This helps prevent accidental tipping and other expensive disasters.

    The higher load point does make it a bit of a chore to get the tube initially loaded. Holding it by the handle in my left hand and bracing it against my shoulder seems to work best for hoisting it up to the saddle. Once there, the right hand is free to guide the dovetail into the saddle and tighten the knobs.

    Getting it out is easier, loosen the knobs and let it slide down the dovetail. But be ready, when it comes free, you want a good grip because as they say, the bigger they are, the harder they fall.

    Otherwise it travels well. For now, I just wrap it in a blanket and then use a seatbelt to strap it into one of the back seats. The carrying handle is well secured so its pretty easy to carry around. Basically, if you're ok with lugging around an EQ6 mount, handling this scope should present no real difficulties.

    Bottom line is that with the mount, counterweights, batteries and all the other stuff I drag around, the whole kit fills my car anyway and weighs in well over a hundred poounds. Thats more than enough for me and probably for most people who use a car for transport. In the end, adding this scope to the existing pile didn't really change the bigger picture and so far there are no problems bringing it out anywhere I would take any other telescope.


    Using the Celestron Off-Axis Guider

    Another new piece of kit I got with the scope is a Celestron Off-Axis Guider. This is their latest model, just released in 2013. I had never used an off-axis guider so there was a learning curve here for sure. Happily, the thrashing and grumbling was less than usual and before long both the DSLR and the SSAG were focused and guiding was underway. Testing it all from the backyard first really paid off because when I finally got out of town, things went suprisingly well.

    The Starshoot autoguider camera is not all that sensitive and preliminary tests from the backyard showed that it can be difficult to impossible to find suitable guide stars for some targets. However, by getting outside the city glare and selecting targets in line with the the Milky Way, I had no trouble finding guide stars bright enough for the SSAG. I didn't try anyting off the beaten track though, so I cannot yet say how easy it is to find guide stars around M51 for example.

    The adjustments are easy to make and the guide camera easily rotates so it's not difficult to find a guide star if one is available. Focusing the guide camera does take a bit of work, but once its focused you can lock it down and it should stay that way between sessions. I also found that if you remove the nosepiece from the SSAG you can screw it directly to the OAG. To get the SSAG in range of the OAG's helical focuser, I used a large spacer supplied with the OAG.

    Ultimately the auto-guider works just fine. I was also impressed with the overall fit and finish of the unit. It's solidly built and has a fair heft to it. It is also bigger and optically longer than other off-axis guiders I've seen advertised. I don't think that's an issue though, Celestron says that with the right spacer from the kit, the guider places the camera at the optimal focal point. I will be getting a more sensitive camera that should make finding guide stars easier but thats more about being able to run two imaging systems than it is about improving on what I've got now.


    Overall impression so far

    So far I'm really happy with this telescope. Between it and my 4" refractor I can now see and take pictures of almost everything realistically available to the amateur. Yes it is a bit big but it actually takes up about the same cargo volume as my other telescopes.

    I did have to put an extension cord on the hand controller for the mount. The original cord is pretty short, but still quite usable with smaller scopes. However, with the big Celestron loaded high up, being tethered close to the mount was like having a blind robot swinging a garbage can at your head. I actually did bump my head a few times on the first few nights in the back yard, so a ten foot extension on the hand controller took care of that. Now it's much easier to run the scope from any position.

    With the snazzy extension cord and a few other bits figured out I expect this scope will work well for me for a long time. I can't see getting a larger one anytime soon, as this is pretty much the most I am willing to carry around. The views are good and the pictures seem to be working so there's nothing to complain about so far. All that's left is to go somewhere really dark and get on with using it.

    David Ritter
    2013-09-03


    I have no affiliation with Celestron, Televue, Baader Planatarium, Antares or any other manufacturer or company mentioned in this article. Nor have I ever received any fees or other forms of financial compensation from any of these these companies, Additionally, I have never received free astronomy gear, hockey tickets or coffee mugs from any the aforementioned companies. Hopefully this review will change all that.

    I did get a free coffee mug and regularly get free calanders and great service from All-Star Telescope in Didsbury, Alberta. Thanks Ken.

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