 Today's video is sponsored by Squarespace. Question that comes up all the time in astrophotography circles is, should city imagers who are interested in narrowband imaging of emission nebulae stick with color cameras or make the switch to a monochrome camera? And it seems like a fairly clear cut question on the surface. And when I was first researching this back in 2017, I went right into a mono and expensive three-nanometer narrowband filters. And I still use those filters, so I don't regret getting anything that I did get back then. But in 2017, this was right before all of these excellent multi-bandpass filters for color cameras were available, like the Radian Triad, the Optalongel Enhance, and now the Amplia ALP-T. So now I think this is a bit more of a complicated question. So in this video, I'm gonna explore this question from a few different angles out loud with you. And then I'm also going to review this new mono camera on the market that I've been testing the past few months. This is the QHY 533M. Hey everyone, this is Nico Carver from Nebula Photos. And since this video is partly a review, let's start with some disclosures. I'm in an agreement with QHY that in exchange for long-term loans of their cameras, I will in exchange test the cameras, provide feedback to them and then also review them. There is no money changing hands and QHY also has no input in what I say in these reviews. The cameras that I currently have on loan from QHY are these two, the QHY 168C and the QHY 533M with the 3S filter wheel. Everything else that I'm gonna be mentioning in this video, if there's anything else, is stuff that I've personally bought with funds from my Patreon campaign, which is the main way that I support this YouTube channel. So thank you very much to all my patrons and to QHY for making this video possible. And that's it for disclosures. So let's move into the first topic of discussion. And I wanna start with something that might seem a little bit basic, but it's actually pretty complex. And that is, what's the difference really between a one-shot color camera and a mono camera? The sensors in one-shot color cameras don't directly sense the color of the light. They're actually the same sensors that are in mono cameras. They're mono sensors. They just sense how bright or dark something is in the scene. And this is why if you open a FITS file from a one-shot color camera directly, it is mono, or another word for that is grayscale. And at first it seems like, well, what's gone wrong here? Why is there no color in the photo for my color camera? Well, color in digital cameras is actually something that is interpolated by software using something called a debayer algorithm. And for that algorithm to work properly, it needs to know the pattern of the color filter array inside the camera. And this color filter array is a physical thing. It's hard to see, but it's made up of tiny little red, green, and blue color filters, one filter over each photo site on the sensor. And the reason that algorithm is called debayer is because the first and still most commonly used pattern for a color filter array is called the Bayer pattern, named after its inventor who worked for Kodak. And the Bayer pattern uses two green filters for every one red filter and one blue filter. And the reason for this has to do with the way that the cones in our eyes work, which generate color in our brain. And the goal is to mimic our eyes color response to get us close to a natural color rendering, which is what works pretty well for normal photography. The downside, which we'll get to is that this means only a quarter of the sensor is set up to receive red light, a quarter of the sensor for blue light, and half the sensor area is for green light. So to sum up the difference between a mono camera and a one shot color camera is with the color camera, there is a fixed, you can't remove it, physical color filter array placed over the sensor with a mono camera, there is no color filter array. So no debairing to make a color image, we actually have to shoot through external filters one at a time and then put all of those data stacks together to make a full color image. And this is why we say one shot color OSC with a color camera because you can literally take one shot and have a color image after you debair it. While with a mono camera, if you just took one shot through one filter, there is no way to colorize that to make it look like a full color image because you just have one color. So you need to use at least two or three filters to get full color with all the color contrasts. So the next question is, what kind of camera is better for narrow band image? And the clear winner here, just in terms of image quality, I think is always going to be the mono camera. And let me explain why. When you're shooting broadband, a one shot color camera is pretty efficient because all of the photo sites on the sensor are receiving light. When you use a single line narrow band filter though, you're blocking 99% of the visible light. And just focusing on one tiny sliver of the visible spectrum. So if that tiny sliver is in the red part of the spectrum, as it would be with an HA or S2 filter, you're letting only those particular red wavelengths pass on to the color filter array. So by the time they get to the color filter array, there are no photons hitting the blue and green filtered photo sites. So you only are using approximately 25% of the sensor when shooting HA or S2. And this is a simplification, but the broad strokes of that are right. With a mono camera, the entire sensor area is being used. So that's a lot more efficient. Now, the introduction of these multi band pass filters designed specifically for color cameras has evened the score a bit between OSC one shot color and mono, because with these we get a lot more efficiency back because we can target both the HA line in the red spectrum and the O3 line, which is in both the green and the blue spectrum at the same time. With mono, you have to target one emission line at a time. You have to use a separate filter for each line when doing narrow band imaging. But with a color camera, with a multi band pass filter, you can actually target and isolate multiple emission lines. And then after you get past the multi band pass filter, it's the, those colors can be separated out using the color filter, right? We can separate out the red response from the blue and green response. You can't do this with mono, right? So you can use these multi band pass filters with mono, but you'll never get a color image out of it. It'll just, because there's no color filter array to separate out the signal. So you just get a grayscale image. So is mono is still better in this case, even though you have to shoot through multiple filters instead of just one? I think yes, because the whole interpolation of the colors using the debayer algorithm, that's not a perfect process. In that process, it's gonna generate some color modeling, some inaccuracies, which you wouldn't get with mono. And also mono is more sensitive to the light since there's less filtration. There's no CFA. There's no color filter array. So you typically see a better cleaner result, more signal with a mono camera, even though you have to shoot through each filter separately, which can take more time. And that better performance means it's easier to go after more difficult objects, like very dim objects in the O3 band, like the squid nebula, for example, which you're seeing here. And so that in a nutshell is the performance debate. Of course, you can get good results with either of these days, but like I said, I always get better, faster results with mono when imaging from border eight or nine. And I wanted to do an actual, like same night performance tests like I usually do with these videos through the same telescope, comparing one shot color to mono, but I've been waiting over a month here and the weather has not cooperated yet. So you'll have to wait for a part two to see that. Next question is, which costs more? Pretty easy. Mono is basically always more expensive to get into. The mono cameras themselves are typically a bit more because it's more of a niche product. So you don't get the economies of scale that you do with color cameras. As an example, the QHY533M is $200 more than the color version. And then with that color version, after you get the camera, you're gonna want a couple filters. I'd say most people at minimum want an IR cut filter, like an Astronomic L2 for doing broadband and then a multi band pass filter like this Optalong L Enhance for narrow band and then maybe a filter drawer for convenience for switching them. On the other hand, with mono, you're gonna want at least red, green and blue filters to do broadband. You're probably gonna want that luminance filter too because LRGB is a cool way to image. Then to do pure narrow band, you need at least the HA filter and the O3 filter. Most people are also gonna want the S2 filter so you can do full Hubble palette and we're already up to seven filters. So in the case of having seven filters to go through, you're probably not gonna want to use the filter drawer. Instead, you're gonna wanna go for an electronic filter wheel for switching between them. So the cost of this is a lot more than a filter drawer. And even if you went with the cheapest filter set, which I believe are the Optalongs, which have seven nanometer band passes for the narrow band filters, the difference between a complete package with the QHY533C versus the M is at least a $500 difference with the monochrome being about a $500 premium. So is that $500 premium if you're doing narrow band imaging from the city worth it? I think absolutely, but you might not have $500 to spend. So I think either way can work, but it is to me worth it for the mono. Another question that is pretty important is which is more of a hassle? And this sort of depends on the person, but with one shot color and a multi band pass filter, you set everything up at the beginning of the night. You get the telescope in focus. You start your imaging run and then there's nothing else to really change. Yes, you should still probably occasionally check focus because focus can shift like if the temperature changes during the night, but that depends a lot on, you know, how stable the temperature is over the night and also your focal ratio with a slower focal ratio not being as big an issue. With mono on the other hand, anytime you change the filter, you know, for red to green or HA to O3, you're most likely gonna have to refocus. Even if a filter set claims to be parfocal, that doesn't mean your telescope is parfocal at all these different wavelengths. So most of us have to refocus when doing mono for each filter change. And if you don't have an automated focuser on your telescope, that means being out there physically refocusing, pausing your imaging run, refocusing at the right time, anytime you change the filter. Another hassle factor is incomplete captures. If you're shooting mono, and let's say you're planning a bi-color HOO style image so you're shooting HA and O3, you start the night shooting H-alpha, then you plan on shooting O3 later when the moon is set, but what actually ends up happening is clouds roll in right when you start shooting O3. If that happens, well then you can't make a full color image because you've only shot the HA. But if instead we've been using a color camera with a multi-bandpass filter that's picking up the HA and the O3 at the same time, then when the clouds roll in, we can still make a full color image with what we got already. So this hassle factor isn't usually a big deal for me personally because with most of my narrow band projects, I'm collecting data over multiple nights. But if you're the kind of imager that likes to get one finished picture per night, then mono might not be for you because it might be occasionally frustrating when you have clouds ruin the later part of a night. Another hassle with mono is each filter needs its own set of flats because anytime you change that physical light path, you're gonna need new flats to get a good calibration. And then when we get to pre-processing because you have all these different sets of flats and lights, you need to calibrate, register and stack on each filter separately before you can combine them all together to get on with processing. So there are some automation tools for this, but it will always still take more time to pre-process mono data than it would one shot color. But once we get past pre-processing, I think most people will agree that mono data is actually much easier to work with because it's cleaner, you can stretch more aggressively, you usually have more signal to work with and so you can play with it more and that's why I still really love it. I just really like processing mono data versus one shot color. So next up, I'm gonna talk about what I like and dislike about this new mono camera, the QHY533M. But before I jump into that, a few words from this video's sponsor, which is Squarespace. When Squarespace offered to sponsor a series of my videos, I was very glad because I'd been putting off revamping one of my websites, nicocarver.com and I knew that I wanted to make it into this like nice portfolio design that could show off my photography but I'd been putting it off because I knew from making lots of websites how long it can take to design a website from scratch. But Squarespace made that process incredibly easy after I transferred over the domain name, I was up and running very quickly because their professional templates and website editor is super easy to use, no coding, what you see is what you get with it and I think it looks very elegant and it just took me one afternoon. I also really like that everything is included. Of course it does responsive design so it looks good on mobile phones or on desktop. I didn't have to search through any confusing plugins to get a really nice contact form that works. It was all part of the template that I chose and if I wanted to add an online shop later I can already tell that would be really easy to do with Squarespace's built-in e-commerce tools. It can handle your inventory, shipping labels, shopping carts, everything is already there for a very reasonable price. So if you're interested in trying out Squarespace use the link in the description of this video and the link is squarespace.com slash Nebula Photos. You'll get a completely free trial and if you like it you can get 10% off your first purchase with the code Nebula Photos. Okay, so now let's review the QHY 533M, a camera I really liked. It's going for $1,159 at the time of recording. Personally I think that is a fair price for this tech. It is a fairly small sensor for deep sky. I'm not sure if you can see that. It's a one inch square sensor so that's smaller than micro four thirds. Here's a graphic I made to show if we were shooting at 300 millimeter focal length this would be the field of view with the 533M in yellow. Here's an APS-C crop sensor camera in green and a full frame camera in pink. And you can see the other thing that sticks out is the aspect ratio of the 533. It's a one to one square while a typical camera is a three by two rectangle. Another interesting thing is while the sensor is much smaller the body size of this camera is actually the same size as my 268M which has a crop sensor. So I'm not sure why they didn't make the 533M body size smaller but I mean it does feel like a premium camera. It weighs 845 grams or 1.8 pounds which is just a little bit less than the 268M which is one kilogram or 2.2 pounds. They made a few design changes to the camera body here. The first one is they added this little metal foot which can be handy for attaching the camera to a dovetail if you wanted to mount a camera lens on the front here. I tried it out, it worked fine especially because the aspect ratio of the sensor is square. So if you have this attached to a dovetail you're not gonna be able to rotate but that's fine because rotation is more important with a rectangular sensor. And speaking of rotation QHY has developed something pretty neat which is this faceplate for the camera that has these little screws so it offers easy rotation. So you can more easily get the sensor square onto the filter wheel and the telescope if you wish to without the need for any kind of like thin spacers to get it exactly in the right orientation. And this faceplate has standard 42 millimeter threads on the front which is different from QHY's bigger cameras which only offer bolt-on connections. If you really wanna get the most out of the QHY system I do highly suggest getting one of their matched electronic filter wheels with their cameras because it's really meant to be a system and you can take advantage of their special cable which connects between the camera and the filter wheel and seems much more robust than just USB. And speaking of this filter wheel it comes with these bolt-on spacers right here that I already have installed and when you put all of this together like this and the camera you have perfect 55 millimeter spacing so you get that's normal back focus requirement for a lot of field correctors, field flatners, coma correctors and then this thread at the end of the spacers stack is 48 millimeter female thread so that's exactly what you want for screwing on to that field flatner or coma corrector and attaching it to the telescope. So everything is in the box ready to go. If you take this whole stack of bolt-on spacers off you can easily switch it out for QHY's 42 millimeter EF adapter which just screws on and it gives you the correct back focus of 44 millimeters for Canon EF lenses. So I tried that out with the Rokinon 135 F2 and the Skywatcher Star Adventure GTI and I loved that combo. I really think that's a great combo in terms of this camera system. In terms of the imaging performance of this camera and looking at the specs this is gonna get pretty nerdy for about 30 seconds here so bear with me. The 533M works exactly like the 268M in high gain mode but unlike the 268M you only get one readout mode rather than four and it's a 14-bit ADC rather than a 16-bit but even with those changes the dual gain amplifier kicks in at gain 56 with both cameras so that is the sweet spot where I would use that gain because you're maximizing dynamic range and low read noise. At gain 56 offset 35 I used Pixinsight's basic CCD parameter script to measure the performance of this camera it had a read noise of 1.647 electrons and a full well capacity of 21,808 electrons. So that's a very low noise sensor that should work very well for narrowband but for me I would use these same settings for broadband too and just shoot shorter exposures. So specifically again those settings are gain 56 offset 35 and I had the cooler set to negative five Celsius which I think is plenty sufficient in terms of cooling this camera because these cameras have such low dark current that with dark frame calibration you really shouldn't have to push the cooling too hard. The important part is that you can match your calibration frames, your darks, your flats, your bias with the exact same temperature as the lights using the set point cooling. QHY said that they guarantee no amp close up to five minute exposures with the latest firmware I haven't really found amp close with any length exposure but I will say just like the 268M this camera is super sensitive to light leaks. So you really have to take your darks in a super dark location and just make sure that there's no possibility of any light hitting a sensor. The reason is just because it's a very sensitive sensor. So to wrap up I'll share some images I've taken with this camera so far with the specs along the right hand side. I've really enjoyed testing this camera for QHY and I'm happy that this camera is now available for sale so you can all go buy it and start taking pictures with it. If you have a question just drop it in the comments below and since this video is clocking in at over 20 minutes long you are now seeing the names of everyone who currently supports this channel over on my Patreon campaign which you can get to by going to patreon.com slash nebula photos. And one of the perks for signing up is you get your name in the credits like you're seeing right now of all long videos over 20 minutes. But there's a bunch of other benefits outside of that including exclusive videos, monthly Zoom chats, a vibrant discord community, monthly imaging challenges with prizes, bi-yearly group imaging projects and the summer targets have just started so you have plenty of time. And then of course a direct way of messaging me with your questions and comments. So if you like my videos you want to accelerate your learning further consider joining us over there it starts at just $1 a month and again the link is patreon.com slash nebula photos. Till next time this has been Nico Carver, Clear Skies.