6.10
#...
·
1
like
|
|---|
|
Hello to all, I typically use my 70mm apo for astro work - its my only AP scope and I have been gathering images for about 8 months. I have about 6 months of guiding under my belt, and the rig works fine. My rig - Mount: NEQ6 Camera: Canon 60D and a new 2600MC pro. Computer: raspberry Pi (ASIair pro) At this point, galaxy season is coming. I want to get a scope with more reach for DSOs. A friend of mine has a c8 edge HD (6 months old) and the dedicated reducer for sale for a good price. My friend bought a larger scope. I have no experience using SCTs, I have been a refractor person up to now. Before this deal came along, I was thinking to buy a 120 mm SW Esprit, but this new offer is literally 40% of the price. Would the Celestron 8 edge HD be OK for DSOs? Anyone with experience with the edge HD for galaxies or thoughts on this is appreciated. Thanks, Ian |
11.44
#...
·
2
likes
|
|---|
|
Hi Ian. I don't know how valid my vote is on this matter, since the largest refracter I own is a William Optics GT81, so I don't know what kind of result you would get from the Skywatcher. I do though own the C8 edge HD with the 0.7 reducer, and I've been very happy with what it can do. To me it the ideal scope for galaxies, since it's easy to set up due to the size, but at the same time you can get some really nice details on those galaxies. The C8 was my entry into the world of AP, so to me it was very important, that it was a rather user friendly telescope. The only mistake I made, was I started out wanting to guide with an OAG. That did not work very well for me due to the small field of view. For a long time I then guided with a Z61, but have now stubbornly moved back to OAG, which now seem to work. (A bit more tricky to find a guide star than on the GT81). Also if you want to image planets and the moon, the C8 is also very capable. I believe that the C8 is a really good quality telescope, that can deliver very impressive results. So I can highly recommend it.  An example of the C8 with a 60Da/ 071MC pro: https://www.astrobin.com/bl5kuh/?nc=user Note that you might be oversampling a little bit with those cameras on the C8. Kind regards and clear skies Dan |
2.39
#...
·
3
likes
|
|---|
| Although I can't do any comparison to any other type of telescope, I can vouch from extensive experience that the 8" EdgeHD is absolutely phenomenal for DSOs. See my profile (newest images) for tons of examples with this scope, and earlier on my profile for comparing it to the ordinary 8se (note the coma, etc.). |
 #...
·
2
likes
|
|---|
|
Hi Ian, Before our small island will be totally isolated, yesterday, I have ordered a C8 XLT for both lunar and galaxies, believing/hoping that is the right choice. I still have a 0.63x reducer in that I do not worry about the image edges. Imaging the moon with a small sensor like that in the ASI290MM should be painless, especially with the Edge. Since the Edge HD 800 is natively fully corrected you won't encounter any issues with elongated stars. If I had the budget I'd go for the Edge HD 800, but it is out of stock anyway. Hope to share C8 images soon. In my view the C8/Edge advantages are:
The disadvantages:
Should you go for the Edge please look at multi-star guiding in PHD's latest development version. For increased rigidity I'd go for the Losmandy-style dovetail since your mount can handle it. Anyway, have fun! Robert |
3.71
#...
·
2
likes
|
|---|
|
I own both an EdgeHD11 and WO GT102 APO. The Edge has the Hyperstar addition as well. The EdgeHD line of scopes produce excellent images on DSOs, but so does the GT102. In fact, I prefer the GT102 to nebulae and star fields as it produces slightly better images over a wider FOV (more contrast as there is no central obstruction). Now here's something to consider when you are getting ready to purchase a scope for DSO imaging. Get a copy of Stellarium or Sky Safari or even Starry Nights, and play around with the imaging tools so you can see just what the FOV is going to be for each OTA/Camera combination. The Edge will have a much more limited FOV than the APO. As Dan stated, the Edge works great for galaxies and smaller nebulae; the APO for the wider stuff. Now my Edge11HD w/Hyperstar has the exact same FOV as the GTO with the flattener/reducer, yet the APO can produce better images (IMHO) albeit requiring longer exposure times. Hyperstar on the Edge 8 is not recommended. |
|
6.10
#... |
|---|
|
Dan, Robert, PP55, and Michael I appreciate all the comments - very helpful. Its especially useful to see the results posted. The used C8 edge HD that I have my eye on already comes with a dedicated reducer, dew shield, etc. I have been the using ASIair pro for the past 6 months with the small apo and it uses a variant of PHD guiding, but its not multi-star.Best, Ian |
|
11.44
#...
·
1
like
|
|---|
|
Hi Ian. I use the ASIAIR pro as well, and I don't have problems with guiding. Just keep in mind, that you need a rather long focal length on you guide scope (preferable 1/3 or better of the image train). Of cause the new feature with multi-star guiding in PHD is better, but it's not a must. Also I would be surprised if The ASIAIR is not updated with that feature in the near future. It's also possible to do planetary with the ASIAIR, but I would suggest, that if you move in that direction to wire up, and use a program like FireCapture instead, since there are so much more you can do. (And it's easy) Regarding the Hyperstar, I was considering that at a certain point, but could understand on various posts, that the C8 may be capable of the Hyperstar, but it's not practical. You need the 9.25 or even the C11 for it to make sense. The camera, wires etc. simply blocks to big a percentage of the mirror. A note to the collimating. The first long period I never collimated the C8. It holds the collimation very very well. I've switched to Bobs knobs now, since I'm planning to use the C8 for a bit of planetary as well. That switch will reduce how long it's holding the collimation. If you are able to buy the whole package with reducer and dew shield from your friend for a reasonable price, I think it's worth considering. Kind regards and clear skies Dan |
5.88
#...
·
3
likes
|
|---|
|
Hi Ian, Yes, the edge 8 is an excellent scope for imaging. I have used it for several images last year (my other scope also being a 70mm refractor). The increased focal length does create challenges.. but this is going to be the case no matter what scope type you use. I recommend using an OAG. For auto focus I have been using the celestron focus motor and its been working well. |
#...
·
1
like
|
|---|
|
Sorry, Ian, I totally overlooked that you can buy the scope including reducer used from a friend. Perhaps you can try before buy, that would be absolutely safe. As the price is good, I'd say grab it :-) Cheers Robert |
|
6.10
#...
·
1
like
|
|---|
I use the ASIAIR pro as well, and I don't have problems with guiding. Just keep in mind, that you need a rather long focal length on you guide scope (preferable 1/3 or better of the image train). Hi Dan, Yes, was thinking about the guide scope... I could use the 70mm apo to guide - its native fl is 420 mm, which would be almost there with the use of the reducer on the C8 edge. Good point about collimating, this is something I always do with my 15" dob, I meant to ask. Best, I |
|
6.10
#... |
|---|
Sorry, Ian, I totally overlooked that you can buy the scope including reducer used from a friend. No worries Robert, I will ask him, great idea. Ian |
|
6.10
#...
·
1
like
|
|---|
James: Thanks James, the OAG would save a lot of mass! |
|
5.88
#...
·
2
likes
|
|---|
Ian Dixon:James: It will also guide better. With my Eq6r, it guides better with the Edge+OAG combination than the 70mm refractor+guide scope combination. I did try using the asi120 and asi224 as a guide cam, but those chips are too small at that FL. It was a challenge finding good guide stars. I switched to a asi178 which has a larger chip and now finding a guide star isnt an issue. |
|
2.39
#...
·
5
likes
|
|---|
|
Yeah I'd also like to cast the vote that you should forget the dream of using a guide scope on an SCT like the EdgeHD, SE, etc., without having distorted stars (and therefore, signal). This is not because of the focal length; when I first started guiding, I got a 70mm guide scope to piggy back and it was a phenomenal piece of equipment, and the guide star was more than adequately sampled, even when imaging at prime focus (2032mm). The problem is that the guide scope will fail to account for the biggest sources of error in the system: differential flexure and mirror movements ("drift" and "flop" ) . I guided very well with that setup but never achieved round enough (I'm picky) stars because of these problems, and they change throughout the night because of the angular differences as the mount tracks. In some instances, I had football-shaped stars with excellent guiding. This is of course because the guider is keeping the star centered according to what the guide camera sees while piggybacked on the telescope, however it can't correct for movement of that system with respect to the imaging scope, nor can it correct for the movement of the mirror in the SCT. I was confident there wasn't TOO much differential flexure (it seemed very solid), however to this day I don't know which problem dominated. Maybe they both did equally. Neither was fixable, however. I had to return the lovely guide scope and move right into off-axis guiding. I use 5-minute subs now, and this would be impossible with the old setup. I keep almost all of them (seeing hurts me more than guiding). Off-axis guiding is challenging. You have a high focal length at the guide camera (few, and dim, guide stars in the field of view, as well as distortion of the stars, being at the edge of the light cone). However it picks up every single problem that the imaging sensor sees and I keep most of my 5-minute subs with razor-sharp, circular stars. In my opinion, the only proper way to even think about off-axis guiding is to use stellarium (free), and program in your specific optics. As mentioned before me above, you can see the focal length and FOV there, but you can also program in the OAG and use the program to plan exactly what angle and center coordinates you'll need for a specific target to guarantee you have a BRIGHT guide star in the field of view of the guide camera. With extreme brevity, the steps are determine ALL equipment in the optical train that you're using (OAG, spacers, rotator, etc.) and get that finalized, get the pick-off prism as far into the train as you can without casting a shadow in your images (this is hard to get optimized- too far out, and your guide stars are noodles...), find your field of view and get that into stellarium, determine the FOV of the guide camera and program that in, determine the distance between the guider and imaging FOVs and program that in (by placing a planet in the guider, taking an image through the imaging camera, plate solving the latter, and moving to the center coordinates in stellarium- then set the distance such that the guider FOV ends up over the planet in stellarium), and finally calibrate and mark the 0deg angle on the scope using plate solving and stellarium again. Yes, this takes some nights of setup. However, I can now choose a target, go to stellarium and plan out the angle and composition for a target that gives me a bright guide star in the pick-off prism, and move the rotator to the correct angle, all during the day. At night, it's as simple as polar aligning, then using my sequence software's "center" feature to center to the coordinates determined in stellarium. My target will be centered, and the guider will see the planned, bright guide star immediately. No fuss. It's a steep learning curve, but truly the only way to guide at high focal length properly, and actually incredibly easy to use once set up. I plan to have a detailed step-by-step for the above process on my website within a week. |
|
6.10
#... |
|---|
Yeah I'd also like to cast the vote that you should forget the dream of using a guide scope on an SCT like the EdgeHD, SE, etc., without having distorted stars (and therefore, signal). Thanks, wish that I could give (your explanation of guiding with an SCT, tightness of the star field with long focal length and OAG, integration and accounting for mirror flop by OAG, etc) this one more likes. Essentially I will need to change to OAG to meet the challenge presented by the design features of the SCT... these are good words of wisdom. Its also having an impact on my ultimate choice re: SCT or bigger frac. Currently I run a 290mm for guiding. James also mentioned the need for a guide camera with a bigger chip. Thus my used SCT "deal" will also necessitate buying an OAG rig with a better camera. I have played around with Skysafari for years, and have been able to program in FOV and angle relative to my rig. All good to know. Ian |
1.43
#...
·
3
likes
|
|---|
Regarding the Hyperstar, I was considering that at a certain point, but could understand on various posts, that the C8 may be capable of the Hyperstar, but it's not practical. You need the 9.25 or even the C11 for it to make sense. The camera, wires etc. simply blocks to big a percentage of the mirror. I don't know where you got your info but shooting HyperStar (HS) on an EdgeHD 8 is very practical (its why Starizona sells an EdgeHD 8 version [v4] HyperStar). The key is you get the correct camera configuration - aka "soda can" (the Atik 460EX. ASI1600, QHY/ASI294, etc.). Obstruction is not an issue if you keep that in mind. As others have suggested, if you go HS then using a guidescope/camera setup is fine since your FOV will be so wide (390mm). The HS is 25 times faster than native! The EdgeHD 8 w/HS is very mount friendly. If you go native (2032mm @f/10) or with a focal reducer (FR) (1422mm @ f/7) you'll have to go with an OAG as the weaknesses of the guidescope will occur (footballs, differential flexure, etc.) At these FLs a good mount is VERY important - an EdgeHD 8 w/FR setup will begin expose your mount's weaknesses, at native it will be very shaky, anything from 11" and above will crush your mount if its mediocre. You will need an excellent (aka $$$$) mount/pier to carry the weight/FL. Don't let the OAG intimidate you...if you have the initiative to do AP, an OAG is just another hurdle that will make you stronger once you get over it. The hardest part will be backfocus. Using an FR will speed things up and make guiding a bit more friendly. Another decision point is what guidecam and spacing you'll have based on OAG you go with. Sometimes you'll luck out. While there are several (at times seemingly major) challenges, and over all more costly than a single good frac and mount of similar FL, the ability to shoot in three configurations on a singe OTA is a benefit. That said, a big frac with a big pixeled camera will get you very sharp images (and a very empty wallet) but you'd need three fracs to do what an Edge can do. What is saved in OTA cost is made up in cameras costs and learning how to manage three configurations on one 'scope can also appear daunting...but it can be done. It all depends on what you want to shoot and how much $$ you wanna spend. Like everything else of value, stubborness and willingness to press through challenges is also required. CS & GB! |
|
1.43
#...
·
2
likes
|
|---|
|
And before I forget, the reason I recently purchased the QHY294MM Pro (also could have gone with the ASI294M) is because it's form factor (a soda can), dual shooting modes (11MP - 4.63um pixels for native and FR config versus 47MP - 2.315um pixels packed into the sensor for HyperStar config) and a 4:3 sensor (fits the smaller image circle versus larger APS-C/Full frame sensors) made sense. One camera on one OTA for three configs. I am also debating getting the ASI2600MM (or QHY version) coming out soon...please don't tell the wife.  CS & GB! |
0.90
#...
·
3
likes
|
|---|
|
I have imaged with several SCTs and other long focal length scopes. I second the opinion that guide scopes don't work well for these, although it is mainly a matter of focal length. Differential flexure of one type of another will likely affect many of the exposures. Some have used guidescopes with their SCTs, but one person I worked closely with admitted he was using exposures of 5 minutes or less, accepted some oblong stars, and was willing to throw away some of his exposures. This is a debated topic, and you can see how it works for you, and I have to say my experience lies in the 2000-3000mm focal length area. Shorter FL may work better with a guide scope and I will be the first to admit that using a guide scope for guiding is much easier in many ways than other solutions. My solution was to use an On axis guider (preferred if you can fit it into the optical path), an off axis guider, or a camera/filter wheel with an integral guiding chip. These methods provided a great yield of subs with round stars. But the smaller FOV of these solutions require another component - a rotator. I love to image galaxies but many lie away from the plane of the Milky Way with few guide stars. Or almost no guide stars. Because I like to image different objects over the night, I needed a controllable way to rotate to select a guide star anywhere in the area of my target at different rotations for each, so a rotator was essential. Good luck on your imaging, and don't hesitate to add your experiences to the topic for all of us to learn from! Frank |
6.89
#...
·
2
likes
|
|---|
|
Hi Ian, I would like to point out that a 8 inch f/12 Classical Cassegrain might be a better option. It is an open tube therefore immune to dew and faster to reach thermal equilibrium. It will deliver better corrected, more contrasty image and since it has a fixed mirror there will be no flip and no shifting which means you can guide traditionally. It will have a Crayford dual speed focuser, that alone makes it better than any unmodified SCT. Overall it will be something much more similar to a 6.5 inch refractor except it will be about half as long or heavy and you can get one for $1000-$1200. This is what I intend to get in a couple of years when I will have the place for a permanent installation. The EdgeHD is a very versatile platform but I understand you need to hunt small DSOs not wide vistas. From a photographic point of view such targets are more similar to planets, I mean there's a small subject at the center of the field which you want to magnify as much as possible, and anything around it is basically waste of space. The reducer or the Hyperstar make the Edge more suitable for wide field. They will not help with a small galaxy in any way whatsoever, if the galaxy can already fit into your frame when you are imaging at f/10, then going f/2 will simply pull more of the surrounding stuff into the field. There's a plus that this helps with image registration and a minus that you introduce aberrations. But as far as the tiny galaxy is concerned, going f/2 was exactly identical to taking its image at f/10 and downscaling it by 5. So the question is which design can deliver the best image for the narrow field that you care about and I think that this is the CC (what RC is for wider fields, CC is for narrow fields). So I guess the Edge is a good choice if you want to make it your single platform. Use it "plain" for tiny DSOs and planets. Might need a barlow for planets. Put a standard f/6.3 reducer and make it equivalent to a fast 8 inch Newt (complete with coma ). Put a Hyperstar and make it equivalent to a refractor like the 70mm you already have, except it will be extremely faster (and much less well corrected). You will probably have to use different cameras (or the ROI feature of your 2600MC) for all that. And learn many things until you are able to use it comfortably. Think of it as really getting 3 telescopes, each with its individual strengths and quirks.But if you are happy with what your 70mm does with wide fields and want to extend your arsenal to include a galaxy hunter, perhaps you should look for something more specialized to that kind of target. Cheers, Dimitris |
3.01
#...
·
3
likes
|
|---|
|
Hi Ian, That’s a tough decision, although I am not sure they fit in the both category. I categorize my OTAs based on their FL, and the esprit 120 FL is half of what the E8HD would give your while reduced. I have both, but haven’t used the esprit 120mm yet as it has been mostly cloudy since I got it recently, but I have done a lot of work with the C8. You can check what I was able to achieve with it in my gallery (propeller to owl are with the edgehd, as well as the crab. All reduced except M101) Here are some ideas that I would have wanted to be aware of, if I were to make a decision:
I hope this helps. Let me know if there is anything else I can help you with Clear skies, Michel |
1.43
#...
·
1
like
|
|---|
| The only fly in the ointment is the fact that the Edge HD 8 does not cover a full frame sensor. The 120 SkyWatcher does. If you ever want to go full frame camera sensor to cover larger deep space objects or to do mosaics, then you are limiting yourself. |
|
6.10
#...
·
1
like
|
|---|
Michel Makhlouta: Hi Michel, Thanks - this is great. Much appreciated. Ian |
|
6.10
#... |
|---|
The only fly in the ointment is the fact that the Edge HD 8 does not cover a full frame sensor. The 120 SkyWatcher does. If you ever want to go full frame camera sensor to cover larger deep space objects or to do mosaics, then you are limiting yourself. *Thanks! Again, that is great to know. Ian |
|
6.10
#... |
|---|
But if you are happy with what your 70mm does with wide fields and want to extend your arsenal to include a galaxy hunter, perhaps you should look for something more specialized to that kind of target. Thanks, I am really happy with the 70mm, its a great little scope. I just want to increase my reach, and increase the number of targets I can catch with a longer fl. Your input is great. Ian |
|
3.71
#...
·
2
likes
|
|---|
| One more recommendation (if you can afford it) is to purchase a ZWO ASI174mm as your guide camera for the OAG. Ever since I replaced my ASI120 with the 174 I have never had to search for a bright star to guide on. I have been able to leave the OAG pickoff prism in the same place for the past year. The wide FOV and sensitivity of the sensor makes this possible. |
