 This is the new ZWO ASI 2600MC Duo. And what makes this camera so neat, as you can see here, is that there are two sensors in one camera body. But why? Well, with deep-sky astrophotography, we often use a tracking mount to keep our camera centered on a celestial object throughout the night. But to keep it really centered on the object without any deviation over long, several-minute exposures with long focal length telescopes, we need to be very, very precise. More precise than actually your average tracking mount can handle. So that's where guiding enters the picture. And with guiding, we typically have a whole other camera called the guide camera, and a whole other apparatus, usually a guide telescope or an off-access guider. And the job of the guiding system is just to lock onto the stars, basically taking very quick exposures, like every second or so, and notice when they move, and then counteract that movement very quickly, sending small messages to the tracking mount, telling it just move a little bit this way or a little bit that way, like fractions of a pixel in one direction or another. Now, the problem with guiding is that there's a lot that can go wrong, actually, especially when you're a beginner. Instead of having to worry about just one telescope and camera, you now have to worry about two, how to focus them, how to get all the settings right. And then you also have to make sure if you're using a guide scope that it's attached really securely, it's not going to loosen up or change position or anything like that over the course of the night. So to get back to the duo, the reason we have two sensors is that the little sensor is your guide camera. Your guide camera is built into the duo, and this means that it uses the same light as your primary camera from your main telescope. So there's now no need for a second guide scope. Now, an OAG, an off-axis guide, also uses the light from your primary telescope, but in a different way. It has a little pick-off mirror that directs the light off axis. That's why it's called that, and it needs to be at a very specific part of your imaging train in order to reach focus. So an OAG has a little bit of setup and tweaking to get it to work right. The duo, since the imaging sensor and the guide sensor are at the exact same focal plane back here, all you have to do is focus once with your main camera, and then you're good to go. You can start guiding. So it's by far the easiest setup if you're using the right telescope. But just like with the other two guiding methods, guide scope or OAG, there are going to be some pros and cons, and the biggest cons with the duo are, one, you need a telescope that can illuminate about a 35 millimeter image circle, and if you happen to combine it with a very slow telescope and very restrictive narrowband filter, then it might not guide properly. So the question to ask yourself before buying the duo is, do these two cons matter in my particular situation? If these cons don't matter to you, then I think this camera is going to be a no-brainer over the 2600 Pro because it's only $200 more. Before I go any further, since this is a review, let me get through a couple quick disclosures. ZWO sent me this ASI 2600 MC duo to review here on the YouTube channel. I have complete freedom to, of course, say whatever I want, no money exchanged hands, and same thing with this ASCAR 103 APO telescope. This isn't the review for this telescope, but the review will be coming soon. But I just thought it was a really good telescope to test this camera with because I have all these additional reducers and things so I can shoot at f4, f6.8, and then see how the focal ratio affects guiding with the duo. And then last disclosure, this SV Bony SV220 was sent to me for review by astrogear.net, which is a great store for affordable astrophotography equipment. And that's all. All the other gear was bought personally or for the channel. When I buy things for the channel, they're with proceeds from my Patreon campaign. So let's start the review with differences between the Pro and the Duo. The obvious difference is the inclusion of the guide sensor in the Duo. And I'll get to that in just a moment, but let's first go through some of the less obvious differences. With the Pro, my camera came with this flat black USB 3 cable for attaching it to a computer to control it. With the Duo, it came with this much thicker and seemingly more durable red-sleeved USB 3 cable. In terms of spacers, the Duo now uses 54 millimeter diameter spacers, while the Pro uses a 42 millimeter and a 42 to 48 millimeter spacer. The reason for the bigger spacers with the Duo is because the faceplate on the camera has changed to accommodate the dual sensor, and that means a bigger light cone needs to illuminate both sensors. So you need bigger spacers. The back focus is the same. So if you leave in the tilt plate, you need about 37.5 millimeters of spacers to reach 55 millimeters, which is a common back focus. And that's what ZWO provides with both cameras. Now with the Pro, the spacer stack ends with 48 millimeter diameter threads, which is very convenient because it's what almost all flatteners and flattener reducers are going to use. The Duo ends with 54 millimeter diameter, but then they provide an inner 54 to 48 millimeter step-down ring so that it will be compatible. But this is my least favorite thing about this kit because it can easily get stuck on the threads of the reducer and then be really hard to get off. And yes, you could use some anti-seize lubricant on the threads, but that's so close to the glass that I think that's a little bit risky. So what I wish ZWO had done instead is provide a 54 millimeter spacer like they did, but also a 54 to 48 millimeter step-down spacer that is one machined piece of metal, because that'd be a lot easier to use with the majority of telescopes you're going to use this camera on. The last and most important change is the Duo incorporates ZWO's latest and greatest guide camera sensor, the ASI 220 mono with four micron pixels right into the camera. And as far as any software is concerned, it just acts like two cameras on your computer. So it's really two cameras for one. If you went with the Pro version of the camera and you wanted the same guide camera, the ASI 220, and a guide scope as well, that's going to cost you about $400 minimum. While the Duo is only $200 more expensive than the Pro. So if you're deciding between these two, it does potentially save you about $200 to go with the Duo. There's one caveat there, which is the setup with the guide camera and scope separate. That's a little bit more flexible, because I could take the guide camera and guide scope and move it to any system. And an example of why you might want to do that is if you upgraded to a different camera, like a full frame camera or a mono camera in the future, then you'd already have the guiding system ready to go. Well, with the Duo, you're now pairing your guiding to this particular one shot color sensor. Now don't get me wrong, it's an excellent sensor. So I don't see it becoming irrelevant anytime soon. But just keep in mind that you're paying more by separating out guiding, but that also gives you more flexibility for future upgrades. The other thing to keep in mind with the Duo is you need a telescope with a large enough image circle that the guide sensor is illuminated. And to keep it simple, I think ZWO just states that the telescope should support a full frame sensor. But that means different things to different people, because it might mean that the telescope is well corrected to the corners of a full frame sensor, meaning round stars all the way to the corners. But very few telescopes do that. What I think it actually means is just that the telescope can illuminate a full frame sensor, even if the stars are a little bit wonky, it's still going to guide. And that opens it up to many more telescopes. But there are still some that you'd want to be careful with. My first thought in order to test this sort of image circle question was their Ryan Short Tube 80, because I know from past experience that it doesn't illuminate a full frame sensor. But unfortunately, I couldn't find the right adapters to get that hooked up to this camera. So what I went with instead was my EFS kit lens, 18 to 55 millimeter Canon EFS lens. This is designed only for crop sensors. And I know from experience, if you do put it on a full frame camera, you do get vignetting. So I thought this would be a good test for the duo since I know this lens can just barely illuminate outside of a crop sensor image circle. So we'll get to that test later in the video. Another series of tests that I did was with filters. So what I tested was no filter, the SV Bony SV 220, which has two seven nanometer band passes at the 03 and HA emission lines. And just for fun, and to really test this thing, I went with a single line three nanometer HA filter from Antlia. This isn't something you normally do with a one shot color camera, because it's always going to be more efficient to use a dual narrow band filter. But I was curious if it would still guide with only three nanometers of HA light coming through. And so I tested these three, the no filter, the SV Bony and Antlia, both at f4 and at f6.8. Now I'm sure I'm going to get comments saying that I didn't cover enough situations. I should have shot f10. I should have shot this and that. But I'm not the only person testing this camera. So I'd advise you next to go check out Ben's review on the narrow band sample because Ben did something very clever. He used aperture masks to test down to f10 with this SV Bony dual narrow band filter, and then also tested with three different telescopes. So it's definitely worth checking out his really extensive review. I'll put the link in the description. All my testing was done with this ZWO AM5 mount. I thought that would be an interesting amount to test on since I found that this AM5 likes short guide exposures best, like half a second. So it seems like that might be a challenge for the duo. And I know a lot of people have the AM5 that might have other ZWO gear. So I also thought it would be relevant. So that's my testing setup right here. For the rest of the video, we're going to be looking at those test results, both the photos and the guide graphs. And I'll be examining these guide graphs which came out of PhD2 using Andy Galasso's PhD2 log viewer, which is free software. And I'll put the link to download that software down in the description. Okay, here we go. So this first guide graph you're seeing is at f4 with no filter. And for all these guide graphs, during the first exposure or so, I'm playing around with the settings, trying to find the settings that I think work best for that particular setup. And in this case, I have in my notes that I settled on gain 300 and 0.5 second exposures. But because I was messing around with things during that first exposure, I'm just going to exclude it from the statistics. And that makes the statistics tell us that the total RMS for a few exposures here, I think I did three or four, is 0.44 arc seconds. So quite good. Really, really good guiding. I mean, I think that's about the best I usually ever get out of the AM5. So f4 with the duo is quite successful. And then in most cases, I'm just going to look at just what I think is a example exposure of what it can do. So either exposure two or exposure three here look pretty good. But let's just go take a look. So here's a single exposure at that setting. This is the elephant trunk. I don't know if you can see it. The vignetting is pretty extreme at f4 with no filter. And I haven't applied a flat. This would mostly go away with a flat. But anyways, if we zoom in on the stars, we can see they're nice and round throughout the frame here. So no issue with f4 and no filter, but I wouldn't expect there to be an issue with those settings. Okay, now we're looking at the SV bony dual narrowband filter. Make that a little easier to see there. And I excluded this first couple exposures where I was messing around with settings. I ended up with a gain of 350 and one second exposures for the guide camera. I thought worked best. You can see the total rms went up a little bit. It went up to point, what does that say, five, three arc seconds. So it didn't go up too much. It basically looked the exact same as with no filter, except there were a few random very short spikes, both in RA and in deck. You know, I've seen these before with the AM5. It recovers so quickly that I don't think they usually show up in your sub exposures. You know, these are five minute subs. And this is like a a little, you know, half a second jump or something. And this is at, you know, 420 millimeters focal length. So I don't expect there to be any issue with the stars not being round. But let's just double check. Yeah, and those stars look a little pixelated. But other than that, nice and round, no problem there. And again, these, these are just raw sub exposures, nothing done to them other than opened up, debared and screen stretched. Okay, now we're looking at the result with three nanometer HA filter in place. And I did have to play around with the settings a little bit. And I found that leaving the exposure length at one second, but increasing the gain all the way to 600 still let me do multi star guiding and it looked pretty good. So at f4, you can use a three nanometer filter with this camera and it works pretty well. The, you know, the total rms went up a little bit 0.71 arc seconds. But perfectly good, you know, for 420 millimeter focal length, you know, this, it worked really, really well considering. So I was impressed by this. I wasn't sure if this was going to work at all. And at f4, it worked quite well. So let's take a look now at the result. And, you know, when you're using a single line narrowband filter, there's nothing in the green or blue channels. So I just extracted the red channel here. But let's look at the stars. Okay, there we go. They all look reasonably round to me. I don't see any, any issues there. Okay, we're now looking at f6.8 and with no filter. Now this was a different night, which I think was not quite as steady as that first night. So I'm not sure how much that's playing into these results. But in any case, I found it that it was a little bit spikier at this slower focal ratio. And, but my total rms was still under an arc second here. It was, you know, 0.99. So still sub arc second guiding, but not quite as good as the, as the f4 result. But you can see at least one sub exposure here, what it was a little bit better with no spikes. Okay, let's look at the result here. Okay, there's the resulting picture with no filter at f6.8. And if we zoom in, those stars do look round. I don't see any kind of elongation. Okay, now here's the SV bony at f6.8. And again, I excluded this part where I was messing with the settings. In this case, I ended up going to gain 400 and one second exposures. And found that the guiding was pretty consistent with no filter or with SV bony filter. You know, it was about the same one arc second guiding here. I think these are just wind gusts, you know. So while I was actually imaging, it looked pretty, looked pretty good. And if we look at the resulting picture, these stars do look nice and round. So at around f7, I think you're going to have no problem with a dual narrowband filter. And this was still picking up multiple stars for multi star guiding. I had no issue there. Now I tried for quite a long time to get the three nanometer filter working at f6.8. And it was just not having it. I could find maybe one star to guide on, but then it would lose the star frequently. You know, sometimes I would have, it would start to look fine and I'd be like, oh, it's gonna, it's working, it's working. And then after about a minute, it would just go, it would not be able to correct anymore. And so, yeah, there was no hope with the three nanometer filter at f6.8. So I didn't get a picture I gave up after a while. This is another attempt. Yep, there's another attempt. This one, again, you can see for about a minute, everything was going fine. Then when it was starting to get off, it could try to correct and it just couldn't do it. We're looking at 75 arc seconds of off there. Okay. And then this last one I'm going to be showing you is the Canon EFS lens. And I had to move around, slew around a little bit until I could find a guide star. I think I needed one that was bright enough that even though I was in like a fairly unilluminated part of the light cone, it could still sort of pick something up. And it did calibrate pretty well. So that gave me hope. But then when it came to actual guiding, it was pretty rocky. This was at gain 600 on a single star with two second exposures to try to get some signal there. And you can see down here at the bottom, I lost the star a number of times, like five times, you know, in pretty quick succession within the first couple of minutes. So not the best, you know, 8.63 arc second guiding. But for 55 millimeter focal length, maybe that's, you know, that's fine. Let's take a look at the image. And there's the image. And yes, indeed for that focal length, I guess we have a little bit of trailing. Actually, I'm not sure. I'm not sure, you know, what is the quality of the lens here and what's trailing, because it looks trailed left to right over here, but it doesn't on this side. So who knows, maybe that maybe this test isn't super scientific, but I thought it was interesting. The point being that if you're using an optic, you know, a lens or a telescope that has a very small light cone and can't illuminate up, you know, 35 millimeters diameter, you're going to have trouble finding bright enough guide stars, you're not going to be able to do multi-star guiding and your results will probably be questionable. So you do sort of need the right telescope for the duo, but I was pretty amazed at how well it could do when you do have the right telescope. So if you have an F4 telescope that supports full frame sensors, you're going to have a great time with the duo. Even if you're at F7, I think it will work in almost all cases, unless you're trying to do something extreme like I was with a three nanometer HA filter. Well, that's it for this one. This has been Nico Carver, Clear Skies.