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Hello, right now I am a happy owner of a Takahashi Epsilon 130. I am thinking about adding a Celestron EdgeHD 11 to my observatory. Its awesome that at Astrobin one can look at pictures other people have made with this telescope before buying it. After studying many EdgeHD11 pictures of various authors, I find that in many pictures even not-so-bright stars all have a distinct halo. Pictures taken with my TAK E130 simply don't have such halos, so I find this a bit disturbing. Are these halos a well-known shortcoming of the EdgeHDs, or even of all SC telescopes ? How significant are these halos to EHD owners here ? Thanks Goetz |
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Hi Goetz, I do not think I have issues with halos IF environmental conditions are good and/or accounted for. For example, I do get halos when I'm not able to deal with excessive dew. Here is an example with EdgeHD11 in Hyperstarv4 configuration: https://www.astrobin.com/8mh3ri/ Let me know if you think halos are excessive in this one. Best, Jim |
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They are absolutely unsignificant Goetz. Forget them. With the resolution of an edge 11 and a fine camera you can humble the CDK users. Cheers, Christoph |
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I have an C11 Edge and also now a SVX152T. I have worked hard to collimate the C11 and work around its issues, notably I added an external focuser (LiteCrawler - highly recommend). I also am in an area which has good seeing; lousy transparency and awful light pollution, but good seeing. I find I can get just slightly better FWHM with the refractor than the C11. The C11 with its 11" vs 6" aperture wins in terms of total integration time needed. But the C11 is ... quirky. First, the reducer that most people use with it can be problematic, especially on a full frame. It is very hard to find a backfocus spot that gets the corners really clean, the stars have slightly oblong shapes even if you work hard on tilt. I think this also may be instance specific as I know a lot of people claim not to have this problem (then again, I suspect they may have crop sensors and/or lower expectations and/or have it obscured by seeing). I find shooting at 2800 without the reducer however produces fairly clean corners. Tilt is both easy and hard to fix -- hard that it is hard to find an adequately dense star field much of the year to actually get a good read on tilt, but easy in that F10 makes for relatively large adjustments, not needing micron level precision. The other issue is that the F10 and 11" aperture tend to require a change in exposure. Diffuse objects follow focal ratio, so F4 is twice as bright as F5.6, etc. But point sources mostly follow aperture, and the better the optics and more focused the more that is true. That means as you increase exposure for diffuse objects at F10, the stars tend to saturate more, and bloat. You can adjust exposure (more subs, less exposure) to accommodate that. Here is an example. This is a very bright star and (optical?) double near M5. Very bright. On the left is the C11 and right is the 152. The 152 has been scaled up to approximately match the C11, so you see more noise due to magnification. The C11 halo is larger, the rays extend further. They are actually a bit more symmetric, the 152 does not bloat evenly for reasons unclear, but they are different. The companion is probably a better example, it is visually larger on the left from bloat (though both nicely split it).  The other aspect that makes me like the C11 less, that may not be much of an issue in the observatory, is that it is physically difficult. Especially with the external focuser, it is VERY back heavy, which means on a saddle it is normally mounted VERY far forward. This gives an awful wind profile, effectively side-winds hit only the forward end, especially if a dew shield is present, which makes for a far greater wind impact than even its 12-13" wide body would normally cause. To offset this I put about 15 pounds of weight on the front of the C11, so it can center better. This heavier weight, the round body and lack of good handles on top, make for more difficult setup and tear down (which I do nightly). in an observatory most of these issues go away (though the potential need for front weights might not, so you may need a beefier mount). Overall I simply have not been able to bring myself to sell it and just use the 152. I get better FWHM on the 152, though very slightly better. But the C11 is almost as good and integrates faster especially for things like globulars (not so much diffuse objects). Oh... external focuser. It helped, but not as much as I hoped. I am not convinced even with the mirror "locked" that there is not some motion in there over time, as tilt seems to change over time (i.e. multiple nights, not over hours). Note that the "locks" are labeled as clutches, not locks - I do not know the physical difference, but apparently older C11 (non-edge) had actual locks, and the Edge does not. The really big win though with the LiteCrawler is now I can change focus (using focus offsets) without restarting guiding or even doing a settle. This means I can image like RRGGBB<dither>[repeat] instead of having to start/stop guiding in between filter changes. This is due to the amazing precision of the focus movement, it does not actually move the guide star. Dither or start/top time adds up a lot over a night. Anyway... quirky is probably a good term. The 130, from what I understand, is also a bit quirky, so you are likely well prepared. Just be sure you have a good mount for it (the AP1100AE I have barely notices it, but I used it on a iOptron CEM70 where it was OK, but very very sensitive to wind). Linwood PS. That's the Blue filter which is the worst. |
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Hi Goetz Using a C11” EdgeHd for many years with a Tak piggybacked on top of it in my observatory, I have only experienced halos under two conditions: 1) near a very bright star in which you have a reflection from the Schmidt corrector plate or lens that holds the secondary mirror at the front of the telescope and 2) reflective, low grade filters. I have imaged with mine at f/2, f/7, and mostly at f/10. It is a wonderful scope. Bruce |
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Interesting discussion but will not comment too much on halos since I live near San Francisco and all bets are off on halos for me. That being said, have been using the C11 for a couple months and compared to my Stellarvue 130 refractor (with very good glass) I see little difference. I just wanted the long focal length and am basically happy. I have a ZWO ASI6200M and have compared images and I do get better resolution for sure with the Edge.... but the fL is 2X+ bigger. Was a breeze to collimate... I did have a Tak 180ED... so anything is easier than that... One known issue I have experienced is that if you use their dew heater that attaches to the aperture some including myself have experiences star distortions. Spikes. PITA as essentially I have to go back to my straps.... they say it is because of the size of the aperture the heating is uneven... Despite total trepidation having and owning expensive Moonlight NightCrawler for the Stellarvue I decided to use the ZWO new electric focuser on the focus know... I was shocked to see it worked fine... drove Steve Brady the developed of FocusMax crazy for a week or so... but it works very well with the "loose" mirror... but I did the math and the CFZ for the C11 is about 220nm.. the Take 180Ed is 17nm... I feel I could get anything focused in that CFZ.... I think this image gives you a fair estimate of what you can do...  Sh2 99 and 100 and LBN 158 Finally I am totally shamelessly copying what Gary Imm does and he sure does well... I have the same Mach1 clunker mount. I was reassured I could just replicate what he did. PS I an a fan of the Sh2 objects and have been reshooting a number lately and you may find the comparison of optics interesting... of course my processing has improved over time too... forget the Tak images... compare with the Stellarvue on the same CMOS. |
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I had many years of success shooting with the EdgeHD 11", a CD camera with a smaller sensor, the 0.7x reducer, and 2016 era Astrodon filters. There were really no problems with star distortions, halos, or chromatic aberrations. The filters are extremely important, so you should stick with a reputable brand that is known to give minimal halos and does not suffer from blue bloat. When I switched to an APS-C camera, I found terrible star distortions in the corners while using the reducer and a low-cost filter set from 2012. I have since switched to Chroma filters, but I did not get to try them with the SCT yet. I'm sure the new filters will help, but I don't think the distortion problem will be gone. I would hate to image at f/10 with the APS-C camera when my old CCD camera has about the same field of view at f/7. The point Linwood is making about diffuse objects vs. stars is quite valid. The SCTs tend to rapidly overexpose bright stars, so you are better off with short exposures and large sensor well depth. Many of my galaxy images shot with long luminance subs have a few ugly, overexposed stars that detract from the image quality. |
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Thanks you all very much for the very helpful comments  It seems that there are several people owning some combination of Tak, SVX and EdgeHD 11. An SVX is indeed the alternative to an EdgeHD 11 for me. The reason I am now going for the Celestron is that the SVX (140) does not fit into my very small observatory shed and building a new one would be a hell of a lot of work. As a Tak user I assume that collimating and de-tilting the HD11 will be easy - as @jerryyyyy has pointed out already from his own experience. The NightCrawler must be a dream of a focuser. Since I positively want to stay with ASIAIR as my computer at the telescope, it is "out-of-scope" for me. Good to hear that ASI's focus motor works as well. I am currently using the ASI 6200MM camera on my Tak. Is it true that at f/2 and f/7 APC-C format is the maximum useful sensor size ? I might get a 2600MC and use the Optolong L-eXtreme filter. Finally, I have seen that ordinary C11 SCs sometimes are equipped with an additional Crayford focuser (e.g. https://www.teleskop-express.de/shop/product_info.php/language/en/info/p3658_Celestron-C11-Astrofoto-Edition---Crayford--Korrektor-und-Off-Axis-Guider.html) . I wonder if this would be feasible on an HD11 as well ? Goetz |
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You could use a Crayford focuser, but if you want the best focuser for the C11, in my opinion, is the Optec Fast Focus SMF system Optec :: FastFocus System (optecinc.com). It is by far the best accessory I have bought for my C11". It takes up no backfocus, essentially removes mirror flop and shifting, and has no backlash to speak of. I had a Moonlite focuser and sold it for the Optec FSMS. With the 6200mm on my Tak and the 2600mm on my C11 in my observatory, it is an ideal combo. Bruce |
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Götz Golla: Hi, Couple points: 1. The 130 SVX FL is 932 from memory and the C11 is 2800... this is a big difference. I had a lot of trouble getting the 6200 flat with the SVX and that was F6.9. The SVX is great and one reason I got it was the Tak was so much trouble and I wanted a wider view. But, you cannot image small galaxys with it at that FL. Jon Talbot has the 152 and that I think comes in at around 1200. But that is a big scope. I had to squeeze mine in a small observatory.... anyway they are apples and oranges.... 2. I have had two Moonlights for the Tak and the SVX. Despite differing mechanisms there were slippage problems with both... they are very tricky devices... the Nightcrawler got touchy with age and I gave up using the rotator because it was so slow... luckily the FOV with the 6200 is so big you can crop as needed. You also need to take into account how the focuser can screw up you collumation, especially if you use the rotator.... unless absolutely perfect... rotate and lose columation.... At the end of the day these are all top scopes and equipment... just cannot do everything.... and you need to dive in to keep everything perfect or close to perfect. JY |
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Bruce Donzanti: Very interesting solution, wow. Thanks for pointing it out. The Fast Focus unit will not work with my ASIAIR and their control software is Windows-only - which is a no-go for me. I would probably need the Fast Focus unit and the FocusLynx Focuser Hub, which than could be accessed via its Web Interface. I would still need (and want) to use the Focus view of the ASIAIR to check the results, which would require an ASI EAF unit attached to the ASIAIR. This could go on the primary focus knob. All in all this would make my observation workflow more complicated because I would have to use a tablet for controlling the ASIAIR and a PC or another mobile device to control the Fast Focus Unit. So, well, for me and the IT architecture of my observatory it looks more like a solution when all else fails. Goetz |
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| As you advance your OTA and equipment, you are one day going to decide that the ASIAir is itself a limiting factor. |
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Linwood Ferguson: I worked with NINA for almost a year and decided to dump it (well, I have it still sitting on my desk) because I found the workflows totally over-engineered. I ended up spending more time with NINAs focussing and PHD2 guiding features than with actually taking images - without any improvement of the final images. Thats why I am now happily back with ASIAIR. Yet you are of course right. It might be necessary to switch back to NINA at some point, better later than sooner..... |
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| I was mostly speaking of the locked ecosystem. If you are happy with their products (and the ones they let you use), I guess that's OK. But a closed ecosystem is inherently limiting. |
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| Götz, the main problem with Crayford focuser is backfocus - they eat up pretty much all of it. The issues with mirror flop can mostly if not completely be mitigated when you ensure in your setup that the last motion of the focuser is counter clock wise, ie against gravity. When you push the mirror - no flop. Mirror shift can be a nuisance when changing filters in combination with an OAG, but can be mitigated with setting up our imaging routine. ASIAIR is a fantastic little device in particular to get you started - but on the long run it is limiting in terms of setup/finetuning your workflow and facilities you can use, the question is only which one of those two factors hit you first. Matthias |
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I am afraid their might be one more issue with the EdgeHD 11 in my particular setup and workflow. I am only at my telescope at the beginning and the end of the observation to open and close the roof of my observatory. Everything else is under complete remote control. Especially filter changes and refocusing after filter changes, meridian flips or changes of the imaging object. My understanding is that the Edge systems have a clutch to lock the mirror after focusing to prevent the mirror from shifting during the observation. Does this mean that for every re-focusing during the night I would have to release the clutch and fasten it again afterwards, requiring my physical presence at the telescope ? Since this would require me to do a 3 min walk back and forth to the observatory shed every time, it would unfortunately be a no-go for my setup. So I hope this it not true - or it would be another case for the Optec Fast Focus SMF system.... |
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| No- not at all. Get your autofocus routine setup and let it run. |
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Bruce Donzanti: good to hear |
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Bruce Donzanti: *At what position do you fix and lock the primary mirror when using the fastFocus. I didn't know this product has been out there for a while and I'm thinking of getting one. Patrick |
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| FYI, my Observatory is automated using ACP/Expert Scheduler that requires the use of Maxim and FocusMax. These are also very complex (and expensive) but they do work. If you are not familiar with Expert Scheduler it automatically prioritizes your observing list. |
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Patrick Graham:Bruce Donzanti: There are a couple of ways to do it. The easiest is to get good focus with the primary mirror like you do now. Then, preset the FF system to its center position at 22,400 steps with the software provided and attach it. At this time, you lock the primary down and do collimation. That is it. |
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Easy enough!! Thanks Patrick |
